Regulation of Arginine and Pyrimidine Biosynthesis in Pseudomonas putida

Abstract

Repression of biosynthetic enzyme synthesis in P. putida is incomplete even when the bacteria are grown in a nutritionally complex environment. The synthesis of 4 of the enzymes of the arginine biosynthetic pathway (N-acetyl-.alpha.-glutamokinase [EC 2.7.2.8], N-acetylglutamate-.gamma.-semialdehyde dehydrogenase [EC 1.2.1.38], ornithine carbamoyltransferase [EC 2.1.3.3] and acetylornithine .delta.-transaminase [EC 2.6.1.11]) were repressed and derepressed, but the maximum difference observed between repressed and derepressed levels for any enzyme of the pathway was only 5-fold (for ornithine carbamoyltransferase). No repression of 5 enzymes of the pyrimidine biosynthetic pathway (aspartate carbamoyltransferase [EC 2.1.3.2], dihydro-orotase [EC 3.5.2.3], dihydroorotate dehydrogenase [EC 1.3.3.1], orotidine-5''-phosphate pyrophosphorylase [EC 2.4.2.10] and orotidine-5''-phosphate decarboxylase [EC 4.1.1.23]) were detected on addition of pyrimidines to minimal asparagine cultures of P. putida A90, but a 1.5- to 2-fold degree of derepression was found following pyrimidine starvation of pyrimidine auxotrophic mutants of P. putida A90. Aspartate carbamoyltransferase in crude extracts of P. putida A90 was inhibited in vitro by (in order of efficiency) PPi, CTP, UTP and ATP, at limiting but not at saturating concentrations of carbamoyl phosphate.