Arginine metabolism in mycoplasma and infected strain L-929 fibroblasts

Abstract

Strain L-929 fibroblasts normally utilize HCO 3 − for the synthesis of their nucleic acid pyrimidines. When infected with Mycoplasma oralis 3 3 A common mycoplasma contaminant of metazoan cells distributed by commercial supply houses. This strain has been identified as M. oralis for us by Dr. R. M. Chanock and Dr. M. L. Somerson, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland. , however, the enzymes arginine deiminase and ornithine transcarbamylase (OTC) are acquired and the guanidino carbon of arginine is utilized in place of HCO 3 − . The pathway of arginine incorporation is via citrulline, carbamylphosphate, and carbamylaspartate. Although pure cultures of M. oralis or hominis possess arginine deiminase and ornithine transcarbamylase activities, neither of these mycoplasma are able to synthesize orotic acid from ureido-C 14 citrulline. It is concluded from these studies that the synthesis of pyrimidines from arginine in M. oralis infected strain L-929 fibroblast cell cultures requires the coordinate utilization of the carbamyl phosphate synthesizing enzymes from the infecting organism and the pyrimidine synthesizing enzymes of the host cell. The metabolism of M. hominis and T-strain Mycoplasma are compared with and contrasted to M. oralis.