A weak link in metabolism: the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis

  title={A weak link in metabolism: the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis},
  author={Enrique Mel{\'e}ndez-Hevia and Patricia de Paz-Lugo and Athel Cornish-Bowden and Mar{\'i}a Luz C{\'a}rdenas},
  journal={Journal of Biosciences},
In a previous paper, we pointed out that the capability to synthesize glycine from serine is constrained by the stoichiometry of the glycine hydroxymethyltransferase reaction, which limits the amount of glycine produced to be no more than equimolar with the amount of C 1 units produced. [] Key Result Detailed assessment of all possible sources of glycine shows that synthesis from serine accounts for more than 85% of the total, and that the amount of glycine available from synthesis, about 3 g/day, together…
The role of energy, serine, glycine, and 1-carbon units in the cost of nitrogen excretion in mammals and birds.
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    Animal : an international journal of animal bioscience
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Division of labour: how does folate metabolism partition between one-carbon metabolism and amino acid oxidation?
The key enzyme for these mechanisms is 10-formyl-THF (tetrahydrofolate) dehydrogenase (both mitochondrial and cytoplasmic isoforms) which oxidizes the formyl group to CO2 with the attendant reduction of NADP(+) to NADPH and release of THF.
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Variation in the glycine conjugation pathway could influence liver cancer, musculoskeletal development, and mitochondrial energy metabolism, and the toxicity of various organic acids.
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Glycine plays an important role in metabolic regulation, anti-oxidative reactions, and neurological function and has been used to prevent tissue injury, promote protein synthesis and wound healing, and improve immunity.
A new perspective on the importance of glycine conjugation in the metabolism of aromatic acids
It will be argued that the major role of glycine conjugation is to dispose of the end products of phenylpropionate metabolism, and it will be explained that the glycine Conjugation of benzoate, a commonly used preservative, exacerbates the dietary deficiency of Glycine in humans.
Amino acid efficiency with dietary glycine supplementation: Part 1
This is the first of a two-paper series reviewing the biochemistry and multifunctional metabolic involvements of glycine and the impacts on physiological efficiency of sulphur amino acids, threonine, arginine and total crude protein, mainly in broilers.
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The fact that urinary excretion of this metabolite is elevated in vegetarians and others consuming relatively low-protein diets strongly suggests that dietary glycine can be rate-limiting for glutathione synthesis in normally fed humans.
Glycine Metabolism and Its Alterations in Obesity and Metabolic Diseases
The present review aims at synthesizing the recent advances in glycine metabolism, pinpointing its main metabolic pathways, identifying the causes leading to glycine deficiency—especially in obesity and associated metabolic disorders— and evaluating the potential benefits of increasing glycine availability to curb the progression of obesity and obesity-related metabolic disturbances.
Amino acid efficiency with dietary glycine supplementation: Part 2
Glycine is a multi-tasking amino acid involved in multiple metabolic and functional systems, including sulphur amino acids, proteins and immunoglobulins syntheses, blood haem and bile production, and its nutrition needs to be critically assessed in the light of modern paradigms of animal welfare, feed-food safety, efficiency, reduced antibiotic application, and eco-sustainability.
Endogenous Synthesis of Amino Acids Limits Growth, Lactation, and Reproduction in Animals.
Quantitative analysis of nitrogen metabolism showed that AA synthesis in animals is constrained by both precursor availability and enzyme activity, which supports the conclusion that the endogenous synthesis of AAs limits growth, lactation, and reproduction in animals.


Branch-point stoichiometry can generate weak links in metabolism: the case of glycine biosynthesis
It may not be possible to ensure that glycine is always synthesized in sufficient quantities to meet optimal metabolic requirements, as a critical weak link is created in glycine biosynthesis by the stoichiometry of the reaction catalyzed by glycine hydroxymethyltransferase.
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Threonine oxidation is increased by glucagon, which also increases threonine's transport and the majority of threonines oxidation occurs through the glycine-independent threonin dehydratase pathway in rat hepatocytes.
Is it time to reevaluate methyl balance in humans?
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Endogenous glycine and tyrosine production is maintained in adults consuming a marginal-protein diet.
The results show that adaptation to a marginal intake of dietary protein consisted of an overall reduction in whole-body protein turnover, net protein catabolism, and the rate of nitrogen excretion, which was sufficient to maintain the endogenous synthesis and hence the supply of glycine and tyrosine.
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It appears that carnitine synthesis is not slowed down by prolonged fasting, that itdoes not completely cover body needs during the first postnatal days, and that it does not decrease in two patients with systematic carnitines deficiency.
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This review is concerned with rates of N flux in the living animal rather than with mechanisms of protein synthesis and breakdown at the cellular level. Methods of measuring protein turnover in the