Regulation of proline catabolism by leucyl,phenylalanyl-tRNA-protein transferase.

A mutant of Escherichia coli lacking leucyl,phenylalanyl-tRNA:protein leucyltransferase, EC 2.3.2.6) exhibited several abnormal growth characteristics relative to the wild type or a revertant when grown with glycerol as a carbon source. All three strains were auxotrophic for proline. The mutant required higher levels of this amino acid than did the other strains to attain a normal growth yield and metabolized exogenous [14C]proline more rapidly. The greater rate of proline utilization was associated with a 4-fold increase in specific activity of proline oxidase. When glucose rather than glycerol was employed as a carbon source, proline oxidase activity was reduced by catabolite repression and the growth ccharacteristics of the mutant were similar to those of the parental and revertant strains. These results suggest that the mutant growth phenotype is due to an altered rate of proline catabolism and constitue evidence for regulation of a specific metabolic pathway by leucyl,phenylalanyl-tRNA-protein transferase.