The role of glutamine in the synthesis of arginine by Lactobacillus arabinosus.

Stokes and Gunness (1) and Lyman et al. (2) found that the amino acid requirements of Lactobacillus arabinosus vary with the composition of the basal medium. Lyman et al. (2) showed that the organism could synthesize arginine if grown in the presence of pyridoxamine and carbon dioxide. Hood and Lyman (3) observed that increased amounts of glutamic acid were necessary for rapid growth in the absence of arginine and that methionine sulfoxide (MSO) inhibited growth. This inhibition was removed by adding glutamine to the medium. It was also shown by these authors that citrulline was more effective than glutamine in replacing arginine in such a medium, indicating that glutamine might be functioning in the synthesis of citrulline from ornithine or some other intermediate. The purpose of this paper is to report the results of further experiments designed to study the mechanism of the utilization of glutamine in the synthesis of arginine by L. arabinosus. The organism was grown in media of varying composition containing N15-labeled glutamine. Arginine was isolated and the distribution of N15 in the molecule was determined.