THE BIOSYNTHESIS OF C14-AMINO ACIDS WITH CHLORELLA

Abstract

The need for radioactive amino acids in biological investigations, as well as the difficulties inherent in the chemical and the biological synthesis of labeled amino acids, has been emphasized recently by Frantz et al. ( 2).These authors suggested reasons why it should be possible to overcome these difficulties through the use of autotrophic bacteria, and they presented data on the biosynthesis by Thiobacillus thiooxidans of seventeen C14-labeled amino acids.The C14-amino acids in the acid hydrolysate of the bacterial protein were adsorbed on and selectively eluted from a starch column.It was stated that the yield of labeled hydrolysate from BaC1403 was about 25 per cent, the yield of separated amino acids was about 15 per cent, and the highest specific activity attained was 1.25 mc. per mM of carbon corresponding to 2.5 mc. per mM of glycine and 11.25 mc. per mM of phenylalanine.The amino acids were prepared in mg.quantities, although exact amounts were not given.Varying quantities of C14-amino acids obtained by other workers include aspartic acid from Lactobacillus arabinosus (3), asparagine from Lupinus angustifolius seedlings (4), glutamic acid from Scenedesmus obliquus (5), glycine (as hippuric acid) from Clostridium cylindrosporum (6), histidine from Xacchuromyces cerevisiae (7), tyrosine from Torulopsis utilis (8), three amino acids (arginine, histidine, lysine) from T. utilis (9), five amino acids from rat liver (lo), thirteen amino acids from X. cerevisiae (II), and fourteen amino acids from T. utilis (12).Fifteen N15-amino acids have been obtained from T. utilis (13).It was the author's purpose to develop practicable procedures for the biosynthesis and isolation of C4-amino acids in amounts sufficient for use in other metabolic experiments.In agreement with Frantz et al. (2), autotrophic organisms with the capacity to utilize efficiently COZ, acetate, glucose, or other readily available carbon compounds were considered to be * Paper 94.For the preceding related paper (Paper 93), see Schieler, McClure, and Dunn (1).