The effect of certain vitamin deficiencies on glycine biosynthesis

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Abstract
Diets containing known amounts of isotopically labeled glycine were fed to rats or guinea pigs for periods of 13-21 days and the isotope content of the glycine isolated from the protein of the mixed viscera at the end of the experiment was determined. The food consumption and changes in body weight were also measured. The amount of glycine synthesized by the 2 species under normal conditions and in the absence of certain vitamins was calculated from the dilution of the fed glycine. Normal glycine biosynthesis by the rat and the guinea pig was 2.7 and 4 m-moles/100 g body weight/ day respectively. Vitamin B12-deficient rats or ascorbic acid-deficient guinea pigs synthesized normal amounts of glycine. Ascorbic acid also had no effect on the synthesis of hippuric acid and formate from serine. Pteroylglutamic acid deficiency resulted in a marked decrease in glycine biosynthesis by the rat and in a reduced conversion of glycine into serine, alanine, aspartic acid and glutamic acid. Results are discussed with reference to the importance of serine and pteroylglutamic acid for glycine biosynthesis.