Experiments on the metabolism of glycine

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Abstract
Unlike other amino acids, glycine is little (8%) or not at all deaminated when incubated with slices or extracts of various organs of the rat, nor is the process aided by fixatives such as NaHSOs and ornithine. Under the same conditions 65-100% of added Gl-alanine was deaminated and the amount was not increased by added glycine. No NH3 and urea formation was observed during the perfusion of liver and kidney of the cat with glycine; all the glycine could be recovered as NH2-N or isolated as the [beta]-naphthalenesulpho-derivative. When glycine was incubated with a mixture of kidney slices or extracts + spleen slices 70-80% of the NH2-N disappeared without a corresponding formation of NH3 or urea; the total N content of the deproteinized fluid was unchanged. A mixture of kidney and liver slices caused no such effect. A condensation of glycine with heat stable compounds under the influence of kidney and spleen enzymes was suggested. O2 consumption of tissue slices and extracts was slightly inhibited by glycine, perhaps by its condensation with oxidizable compounds, protecting them from oxidation. Under the same conditions the oxidation of dl-alanine corresponds to the theoretical amt. required for oxidative deamination. Glycocyamine caused a disappearance of NH2-N similar to that produced by kidney and spleen Kochsaft when added to glycine and mixtures of tissue slices. When incubated with heart tissue in presence of glycocyamine glycine produced a small amount of creatine and NH3. A scheme was suggested for the condensation of glycine with glycocyamine to form creatine. 40-60% of the NH2-N disappeared when glycine was anaerobically incubated with kidney slices or kidney extract in presence of cozymase or pyruvate; the latter partly disappeared simultaneously, perhaps with the formation of keto compounds; NH3-, amide-, purine- and total N remained unchanged. Pyruvate anaerobically incubated with glycine in presence of boiled kidney extract, even in absence of tissue, induced a small disappearance of NH2-N, but none in the absence of tissue under aerobic conditions. The possible metabolic pathways of glycine were discussed with special reference to amino-transfer. The influence of cozymase (from Kochsaft) might point to a link between dehydrogenase systems concerned with the formation of keto-compounds (pyruvic acid, oxaloacetic acid, etc.), and the above-described condensation of glycine with such compounds. Glycine might shift the equilibrium in the direction of increased oxidative production of keto-acids, thus explaining its well-known specific dynamic effect.