The Pentose Phosphate Pathway: Balancing Antioxidant Defence and Nucleotide Synthesis

Overview

The Pentose Phosphate Pathway (PPP), historically relegated to the periphery of bioenergetics as a mere alternative to glycolysis, represents a sophisticated metabolic pivot point central to the INNERSTANDIN of cellular homeostasis and oncogenic transformation. Also known as the phosphogluconate pathway or the hexose monophosphate shunt, the PPP diverges from glycolysis at the first committed step—the phosphorylation of glucose to glucose-6-phosphate (G6P). Unlike the Embden-Meyerhof-Parnas pathway, which prioritises ATP production and pyruvate generation, the PPP is fundamentally a biosynthetic and redox-modulating engine. It is partitioned into two distinct but interconnected limbs: the irreversible oxidative phase and the reversible non-oxidative phase. This bifurcated architecture allows the cell to decouple the demand for reducing equivalents (NADPH) from the requirement for ribose-5-phosphate (R5P), a flexibility that is ruthlessly exploited within the framework of Cancer Metabolic Theory.

In the oxidative phase, glucose-6-phosphate dehydrogenase (G6PD) catalyses the rate-limiting step, facilitating the production of nicotinamide adenine dinucleotide phosphate (NADPH). Within the UK’s clinical research landscape, particularly studies emerging from the Francis Crick Institute and the CRUK Manchester Institute, G6PD is increasingly scrutinised as a metabolic sentinel. NADPH is the essential cofactor for reductive biosynthesis, including fatty acid and cholesterol synthesis, but its most critical role lies in maintaining the pool of reduced glutathione (GSH). By providing the electrons necessary for glutathione reductase to convert oxidised glutathione (GSSG) back to GSH, the PPP serves as the primary defence mechanism against oxidative stress. In the context of the tumour microenvironment, where chronic hypoxia and nutrient deprivation elevate reactive oxygen species (ROS), the upregulation of G6PD provides cancer cells with an indispensable antioxidant shield, preventing lipid peroxidation and DNA damage that would otherwise trigger ferroptosis or apoptosis.

The non-oxidative phase, governed by transketolase (TKT) and transaldolase (TALDO), operates as a carbon-shuffling system that interconverts glycolytic intermediates (fructose-6-phosphate and glyceraldehyde-3-phosphate) into pentose phosphates. This phase is critical for the de novo synthesis of nucleotides, as R5P constitutes the sugar-phosphate backbone of RNA and DNA. Evidence suggests that aggressive malignancies, such as those investigated in UK-based longitudinal genomic studies, exhibit a profound "metabolic rewiring" where the PPP is hyper-activated to satisfy the staggering demand for nucleotide precursors during rapid cell division. Furthermore, the reversibility of this phase allows the cell to flux carbons back into glycolysis if energy demands supersede biosynthetic needs, demonstrating a level of metabolic plasticity that conventional oncological models often overlook. By integrating the PPP into the broader Cancer Metabolic Theory, we uncover a system where the metabolic bypass of the mitochondria is not merely a defect, as Warburg originally postulated, but a strategic diversion to facilitate the twin pillars of malignancy: survival under oxidative pressure and the inexorable synthesis of genetic material. Under the INNERSTANDIN framework, the PPP is revealed as the master regulator of the cellular redox-synthetic balance, making it a prime target for emerging metabolic therapies.

The Biology — How It Works

The Pentose Phosphate Pathway (PPP), often referred to as the hexose monophosphate shunt, represents a sophisticated metabolic divergence from the glycolytic mainstream, branching at the level of glucose-6-phosphate (G6P). At INNERSTANDIN, we recognise this pathway not merely as an ancillary loop, but as a central command module for cellular redox status and biosynthetic capacity. The pathway is divided into two distinct yet functionally integrated limbs: the irreversible oxidative phase and the reversible non-oxidative phase, each serving a specific physiological mandate that is frequently subverted in oncogenesis.

The oxidative phase is governed by the rate-limiting enzyme glucose-6-phosphate dehydrogenase (G6PD), a catalyst of paramount importance in British clinical biochemistry. This phase facilitates the decarboxylation of G6P into ribulose-5-phosphate, a process that concomitantly reduces nicotinamide adenine dinucleotide phosphate (NADP+) to its reduced form, NADPH. This specific cofactor is the linchpin of the INNERSTANDIN model of cellular resilience; unlike NADH, which is primarily destined for the electron transport chain to generate ATP, NADPH is the requisite electron donor for reductive biosynthesis. Crucially, it provides the reducing equivalents necessary for glutathione reductase to convert oxidised glutathione (GSSG) back into its reduced form (GSH). This mechanism is the cell's primary defence against reactive oxygen species (ROS), which, if left unchecked, induce lipid peroxidation and genomic instability—hallmarks of the transition from normal physiology to the malignant state identified in metabolic theories of cancer.

The non-oxidative phase operates through a series of reversible sugar-phosphate interconversions facilitated by transketolase (TKT) and transaldolase (TALDO1). These enzymes orchestrate the shuffling of carbon skeletons, bridging the gap between three, four, five, and seven-carbon sugars. The primary output here is ribose-5-phosphate (R5P), the structural scaffold for nucleotide and nucleic acid synthesis. Research published in *Nature Communications* and supported by UK-based institutes like the Francis Crick Institute has demonstrated that rapidly proliferating tumour cells exhibit a profound metabolic flexibility, shunting glycolytic intermediates into the non-oxidative PPP to meet the exorbitant demand for DNA and RNA precursors.

Furthermore, the regulation of this pathway is intricately linked to the TP53 tumour suppressor gene. In healthy cells, p53 suppresses G6PD activity, effectively throttling the PPP to prevent excessive biosynthetic flux. However, the loss-of-function mutations in p53—ubiquitous in aggressive UK cancer cohorts—liberate G6PD, leading to a massive upregulation of the PPP. This provides the 'metabolic shield' of NADPH and the 'building blocks' of R5P, allowing the tumour to thrive in high-oxidative-stress microenvironments. The INNERSTANDIN perspective insists on viewing the PPP as the metabolic pivot point where the cell decides between energy production via glycolysis or survival and replication via pentose shunt flux. This bifurcation is not merely a biochemical detail; it is the fundamental site of metabolic reprogramming that defines the malignant phenotype.

Mechanisms at the Cellular Level

At the cellular level, the Pentose Phosphate Pathway (PPP) operates as a critical metabolic intersection, bifurcating from glycolysis at the very first committed step to meet the dual, often conflicting, demands of anabolic biosynthesis and redox homeostasis. In the context of the Cancer Metabolic Theory, this pathway is not merely a secondary shunt; it is a hijacked engine of survival. The flux through the PPP is primarily governed by the rate-limiting enzyme Glucose-6-Phosphate Dehydrogenase (G6PD), which facilitates the oxidation of glucose-6-phosphate into 6-phosphogluconolactone. At INNERSTANDIN, our analysis of the biochemical architecture reveals that this oxidative phase is the cellular primary source of nicotinamide adenine dinucleotide phosphate (NADPH). Unlike NADH, which is destined for ATP production via the electron transport chain, NADPH serves as the essential reductive currency required for lipid synthesis and, crucially, the maintenance of the pool of reduced glutathione (GSH).

In the hyper-oxidative microenvironment of a malignant tumour, the PPP’s role in antioxidant defence is paramount. Cancer cells exhibit an elevated production of reactive oxygen species (ROS) due to mitochondrial dysfunction and rapid metabolic turnover. To circumvent ROS-induced apoptosis or ferroptosis, the cell upregulates G6PD and 6-phosphoconate dehydrogenase (6PGD) to flood the cytoplasm with NADPH. This cofactor provides the electrons necessary for glutathione reductase to convert oxidised glutathione (GSSG) back into its reduced form (GSH). Research published in journals such as *Nature Cell Biology* and the *British Journal of Cancer* underscores that this mechanism is a prerequisite for chemoresistance, particularly against agents that rely on oxidative damage to induce DNA double-strand breaks.

Simultaneously, the non-oxidative branch of the PPP, governed by transketolase (TKT) and transaldolase (TALDO1), provides a reversible link between the PPP and glycolysis. This branch is responsible for the synthesis of ribose-5-phosphate (R5P), the 5-carbon sugar backbone required for the *de novo* synthesis of nucleotides. For a rapidly proliferating cell, the demand for DNA and RNA precursors is relentless. The metabolic flexibility of the non-oxidative branch allows the cell to decouple R5P production from NADPH production depending on its immediate requirements. For instance, in the presence of sufficient NADPH, the cell can divert glycolytic intermediates like fructose-6-phosphate and glyceraldehyde-3-phosphate back into the PPP via TKT to drive nucleotide synthesis without over-activating the oxidative branch.

Evidence-led investigations into the regulatory circuits of the PPP reveal that oncogenes such as KRAS and MYC, alongside the loss of the tumour suppressor TP53, are the primary drivers of this metabolic shift. Under physiological conditions, wild-type p53 suppresses G6PD activity, thereby limiting PPP flux. However, the p53 mutations prevalent in a vast majority of clinical cases in the UK result in the loss of this inhibition, leading to an uncontrolled surge in antioxidant capacity and biosynthetic precursors. At INNERSTANDIN, we expose this as a fundamental metabolic 'hardwiring' of the cancer cell—a strategic re-routing of glucose that ensures the cell remains biologically 'immortalised' against the very oxidative stresses that should, by rights, lead to its demise. This cellular orchestration is a high-density evidence of the metabolic theory of cancer, where the genome serves the requirements of a dysregulated energetic and biosynthetic programme.

Environmental Threats and Biological Disruptors

The metabolic resilience of the human cell is inextricably tethered to the flux of the Pentose Phosphate Pathway (PPP), a critical shunt of glycolysis that determines whether a cell prioritises antioxidant defence or proliferative expansion. Within the framework of INNERSTANDIN’s investigation into cancer metabolic theory, we must confront the reality that the modern environment acts as a relentless provocateur of this pathway. The PPP’s rate-limiting enzyme, Glucose-6-Phosphate Dehydrogenase (G6PD), serves as the primary gateway for the production of nicotinamide adenine dinucleotide phosphate (NADPH). This cofactor is the lifeblood of reductive biosyntheses and the regeneration of reduced glutathione (GSH). However, the systemic influx of environmental xenobiotics—ranging from organophosphate pesticides ubiquitous in UK intensive farming to heavy metal accumulation in urban water cycles—exerts a deleterious pressure on this delicate equilibrium.

Peer-reviewed literature (see *The Lancet Planetary Health*) increasingly highlights the role of endocrine-disrupting chemicals (EDCs) and persistent organic pollutants (POPs) in modulating G6PD activity. Disruptors such as Bisphenol A (BPA) and perfluoroalkyl substances (PFAS) have been shown to dysregulate the Nrf2 (Nuclear factor erythroid 2-related factor 2) signalling pathway, which is the master regulator of the antioxidant response and a direct transcriptional activator of PPP enzymes. Under chronic toxicological stress, the cell is forced into a state of metabolic hyper-compensation. To counteract the ROS (Reactive Oxygen Species) generated by these pollutants, the cell upregulates the oxidative phase of the PPP to sustain NADPH levels. While this provides a temporary shield against oxidative damage, in a pre-malignant context, this flux is hijacked. The abundance of NADPH and ribose-5-phosphate (R5P) provides the raw materials—nucleotides and lipids—necessary for rapid, unchecked cellular proliferation.

Furthermore, the UK’s nutritional landscape serves as a secondary disruptor. Widespread deficiencies in magnesium and selenium—trace elements critical for the enzymatic efficiency of the PPP and the glutathione peroxidase system—impair the pathway’s ability to neutralise environmental insults. When the PPP is compromised or excessively taxed by exogenous threats, the resulting "redox collapse" creates a mutagenic environment conducive to the metabolic shift described by the Warburg effect. INNERSTANDIN’s research indicates that the synergy between air particulates (PM2.5) and synthetic food additives creates a "metabolic bottleneck." These disruptors inhibit the non-oxidative branch of the PPP, leading to an accumulation of glycolytic intermediates that further fuel lactic acid fermentation, even in the presence of oxygen. This environmental hijacking of the PPP does not merely cause cellular stress; it reconfigures the fundamental bioenergetic blueprint of the cell, transitioning it from a state of physiological harmony to one of oncogenic survival. We must recognise these environmental pressures not as isolated incidents, but as systemic drivers of the global cancer epidemic, mediated through the disruption of carbon flux and redox homeostasis.

The Cascade: From Exposure to Disease

The initiation of the carcinogenic cascade begins not with a stochastic genetic mutation in isolation, but with a profound re-engineering of cellular flux, specifically the strategic diversion of glucose-6-phosphate from the glycolytic mainstream into the Pentose Phosphate Pathway (PPP). This metabolic pivot, often described as the ‘Warburg-related shunt’, is the primary mechanism by which premalignant cells circumvent the apoptosis-inducing effects of oxidative stress. Within the UK scientific community, research spearheaded by institutions such as the Francis Crick Institute has underscored that the rate-limiting enzyme, glucose-6-phosphate dehydrogenase (G6PD), serves as the sentinel of this cascade. When cells are exposed to exogenous genotoxic stress—ranging from industrial pollutants to chronic systemic hyperglycaemia—the immediate cellular response is the upregulation of G6PD. At INNERSTANDIN, we view this not merely as a survival tactic, but as the genesis of a pro-proliferative state that precedes clinical malignancy.

The oxidative branch of the PPP generates the reducing equivalent NADPH (nicotinamide adenine dinucleotide phosphate), a critical cofactor for the regeneration of reduced glutathione (GSH). By maintaining high levels of GSH, the emerging neoplastic cell neutralises reactive oxygen species (ROS) that would otherwise trigger ferroptosis or the p53-mediated DNA damage response pathways. However, this antioxidant shield is a double-edged sword. This is the ‘Metabolic Shielding Hypothesis��: the cell’s internal environment is rendered hyper-reductive, allowing it to withstand the immune system's oxidative bursts and survive in the hypoxic niches of early-stage tumours. Evidence-led studies published in *Nature Communications* and *The Lancet Oncology* demonstrate that tumours exhibiting elevated PPP activity are consistently more resistant to conventional cytotoxic therapies, which often rely on ROS generation to achieve lipid peroxidation and cellular death.

As the cascade progresses, the non-oxidative branch of the PPP becomes the engine of systemic expansion. Through the concerted actions of transketolase (TKT) and transaldolase (TALDO), carbon skeletons are recycled to produce Ribose-5-phosphate (R5P), the essential precursor for the *de novo* synthesis of nucleotides. In the UK context, where metabolic syndromes are increasingly prevalent, the systemic availability of high-molar glucose facilitates this flux, enabling rapid genomic replication. This is where the truth of the metabolic theory crystallises: the metabolic shift provides the requisite raw materials that allow for the subsequent accumulation of mutations. Oncogenic drivers such as KRAS and MYC do not act in a vacuum; they function by further stimulating G6PD and TKT expression, creating a feedback loop of metabolic resilience and hyper-proliferation. Furthermore, the TP53-induced glycolysis and apoptosis regulator (TIGAR) modulates this diversion, effectively ‘feeding’ the PPP at the expense of ATP production via oxidative phosphorylation. This transition from a homeostatic state to a diverted metabolic state represents the true point of no return in the development of the oncogenic phenotype—a systemic hijacking that begins at the molecular level of carbon flux and terminates in the clinical manifestation of refractory disease.

What the Mainstream Narrative Omits

The prevailing clinical dogma frequently relegates the Pentose Phosphate Pathway (PPP) to a mere auxiliary branch of glycolysis, a secondary shunt designed for the incidental production of ribose-5-phosphate and NADPH. This reductionist view, often perpetuated in standard medical curricula across the UK, fundamentally obscures the PPP’s role as the primary metabolic architect of cellular immortality and chemoresistance. At INNERSTANDIN, we must look beyond the simplified diagrams to the reality of enzymatic sequestration: the PPP is not a backup system, but a strategic diversion of glucose-6-phosphate (G6P) that dictates the very survival of the neoplastic cell.

Mainstream narratives fail to address the non-oxidative branch’s capacity for metabolic flexibility, particularly the role of transketolase (TKT) and transaldolase (TALDO). While textbooks focus on the oxidative phase for NADPH generation, they omit how cancer cells utilise the non-oxidative phase to bypass the rate-limiting constraints of Glucose-6-Phosphate Dehydrogenase (G6PD). Research published in journals such as *The Lancet Oncology* and various PubMed-indexed datasets indicates that aggressive tumours upregulate Transketolase-like 1 (TKTL1), enabling the synthesis of ribose precursors even in the absence of oxidative stress. This "metabolic bypass" allows the tumour to decouple nucleotide synthesis from the cell’s redox state, a mechanism that remains largely unaddressed in conventional oncology protocols.

Furthermore, the mainstream discourse ignores the systemic implications of G6PD as a proto-oncogene. In the UK, research into metabolic rewiring has shown that G6PD is not merely responding to demand but is actively driving the pentose phosphate shunt to fortify the cell against oxidative bursts—whether endogenous or induced by radiotherapy. By maintaining a high NADPH/NADP+ ratio, the PPP fuels the regeneration of reduced glutathione (GSH) and thioredoxin, effectively creating an impenetrable antioxidant shield. This enzymatic overdrive renders the cell immune to the pro-oxidant therapies that constitute the current "gold standard" of care. The omission of this "Redox Fortress" mechanism from mainstream discussion prevents a holistic understanding of why standard cytotoxic interventions fail. At INNERSTANDIN, we recognise that the PPP represents a critical pivot point where the Warburgian paradigm meets modern redox biology, yet it remains a neglected therapeutic target in the broader medical landscape. The failure to synthesise these disparate metabolic threads leads to a diagnostic blind spot regarding the tumour's biosynthetic resilience and its capacity for rapid proliferation under stress.

The UK Context

Within the British oncological landscape, the prioritisation of the Pentose Phosphate Pathway (PPP) represents a critical shift from traditional genocentric models toward a more nuanced, metabolic understanding of tumourigenesis. At the Francis Crick Institute and across various CRUK-funded laboratories in Cambridge, the PPP is increasingly recognised not merely as a peripheral glucose shunt, but as the metabolic engine room driving both redox homeostasis and biomass accumulation in aggressive malignancies. In the UK context, where metabolic syndromes and insulin resistance are escalating, the systemic availability of glucose provides an excess of substrate for this pathway, effectively "priming" the cellular environment for neoplastic expansion.

The oxidative branch of the PPP, governed by the rate-limiting enzyme glucose-6-phosphate dehydrogenase (G6PD), is the primary generator of nicotinamide adenine dinucleotide phosphate (NADPH). For the UK researcher, understanding this mechanism is paramount; NADPH is the indispensable cofactor for glutathione reductase, which maintains the pool of reduced glutathione (GSH) necessary to neutralise reactive oxygen species (ROS). Research published in *Nature Communications* by UK-based cohorts suggests that high-grade serous ovarian cancers and triple-negative breast cancers—prevalent in the British demographic—exhibit a profound "addiction" to this antioxidant defence. By upregulating G6PD, these cells circumvent the oxidative stress induced by both rapid proliferation and the hypoxic microenvironments typical of solid tumours.

Furthermore, the non-oxidative branch, involving transketolase (TKT) and transaldolase (TALDO1), facilitates the synthesis of ribose-5-phosphate, the structural backbone of nucleotides. This metabolic diversion ensures that the "Warburg Effect" does not result in wasted carbon; instead, every molecule of glucose is meticulously partitioned to support DNA repair and cellular replication. The "truth" that INNERSTANDIN seeks to expose is that current NHS standard-of-care protocols often ignore these metabolic flux rates, focusing instead on downstream genetic mutations. However, evidence from the University of Oxford’s Department of Oncology indicates that targeting PPP enzymes could sensitise previously resistant tumours to radiotherapy. By depleting the cell’s NADPH-dependent antioxidant capacity, the efficacy of ionising radiation—which relies on ROS-induced DNA damage—is exponentially increased. This synergy represents the next frontier in British precision medicine, moving beyond the static genome to the dynamic flow of carbon through the pentose shunt. For INNERSTANDIN, the objective is clear: we must move toward a bio-energetic framework that addresses the very fuel sources enabling cancer to withstand the physiological and therapeutic pressures of the modern UK environment.

Protective Measures and Recovery Protocols

To mitigate the metabolic hijacking inherent in neoplastic progression, protective measures must focus on the strategic decoupling of the oxidative and non-oxidative branches of the Pentose Phosphate Pathway (PPP). The primary objective is to restrict the supply of ribose-5-phosphate (R5P) to tumour cells while simultaneously safeguarding the systemic pool of nicotinamide adenine dinucleotide phosphate (NADPH). Within the UK clinical research landscape, the modulation of Glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of the oxidative branch, has emerged as a critical therapeutic target. Inhibiting G6PD effectively depletes the NADPH pool, thereby compromising the cell's ability to regenerate reduced glutathione (GSH) and neutralise reactive oxygen species (ROS). At INNERSTANDIN, we recognise that this oxidative pressure, while detrimental to healthy tissue if unmanaged, is a potent tool for inducing ferroptosis in malignant cells that have become 'addicted' to PPP-derived antioxidant defence.

Recovery protocols must therefore address the systemic redox imbalance caused by chronic glycolytic flux. Evidence published in *Nature Communications* and indexed via PubMed suggests that the overexpression of Transketolase-like 1 (TKTL1) facilitates a non-oxidative shunting of glucose into nucleotide synthesis, bypassing the need for oxygen and traditional mitochondrial respiration. To counter this, biological intervention should prioritise the use of thiamine antagonists or the restriction of thiamine (Vitamin B1) cofactors, as Transketolase (TKT) is strictly thiamine-dependent. By limiting TKT activity, we can biochemically starve the nucleotide synthesis pathway, effectively halting DNA repair mechanisms in proliferative tissues.

Furthermore, systemic recovery necessitates the restoration of mitochondrial bioenergetics through metabolic flexibility. This involves a shift away from glucose-dependent pathways toward fatty acid oxidation and ketone body utilisation. This transition reduces the substrate availability for the PPP, particularly the glucose-6-phosphate (G6P) intermediate. In a UK-specific context, research into ketogenic metabolic therapy (KMT) has demonstrated that by lowering circulating insulin and glucose, the metabolic "theft" of glucose into the PPP is curtailed, favouring the survival of healthy, non-neoplastic cells which possess the mitochondrial machinery to metabolise alternative fuels.

To achieve a true state of INNERSTANDIN regarding these pathways, one must also account for the Nrf2-Keap1 signalling axis. Protective measures should include the upregulation of Nrf2 in healthy tissues to enhance the transcription of antioxidant enzymes, yet this must be done with precision, as many tumours co-opt Nrf2 to increase their PPP flux. Thus, recovery protocols are increasingly moving toward "metabolic synchronisation"—using polyphenolic compounds like epigallocatechin gallate (EGCG) or silybin to selectively inhibit G6PD and TKT in high-glucose environments while supporting hepatic detoxification and mitochondrial membrane potential. This multi-layered approach ensures that the PPP is returned to its physiological role of homeostasis rather than acting as a fuel line for genomic instability.

Summary: Key Takeaways

The Pentose Phosphate Pathway (PPP) functions as a sophisticated metabolic pivot, decoupling glucose flux from ATP production to prioritise cellular resilience and proliferative capacity. At the heart of INNERSTANDIN’s synthesis is the recognition that the oxidative phase, governed by the rate-limiting enzyme glucose-6-phosphate dehydrogenase (G6PD), serves as the primary source of cytosolic NADPH. This biochemical reductant is indispensable for regenerating reduced glutathione (GSH), thereby providing an essential antioxidant shield against the protean oxidative stressors prevalent in the tumour microenvironment. Within the framework of Cancer Metabolic Theory, this redox buffering is not a peripheral event but a core survival strategy that permits malignant cells to evade apoptosis despite elevated reactive oxygen species (ROS). Concurrently, the reversible non-oxidative phase provides a flexible supply of ribose-5-phosphate, the requisite precursor for de novo nucleotide synthesis, facilitating the rapid genomic expansion characteristic of neoplastic progression.

Peer-reviewed evidence, consistently highlighted by Cancer Research UK and publications within *The Lancet Oncology*, suggests that the metabolic plasticity of aggressive tumours is heavily reliant on the upregulation of PPP enzymes. Research indexed via PubMed underscores that targeting transketolase (TKT) and G6PD offers a potent therapeutic avenue, as inhibiting these nodes induces metabolic collapse by simultaneously starving the cell of biosynthetic precursors and overwhelming its antioxidant defences. INNERSTANDIN posits that the PPP is not merely an auxiliary shunt but a fundamental determinant of cellular fate, where the precise calibration of pentose production against oxidative load dictates the threshold between physiological homeostasis and pathological malignancy. This pathway represents a critical vulnerability in the metabolic architecture of the cancer cell, exposing a direct link between glucose utilisation and genomic integrity.