Control of enzyme synthesis in the arginine deiminase pathway of Streptococcus faecalis

Abstract

The formation of the arginine deiminase pathway enzymes in Streptococcus faecalis ATCC 11700 was investigated. The addition of arginine to growing cells resulted in the coinduction of arginine diminase (EC 3.5.3.6), ornithine carbamoyltransferase (EC 2.1.3.3), and carbamate kinase (EC 2.7.2.3). Growth on glucose-arginine or on glucose-fumarate-arginine produced a decrease in the specific activity of the arginine fermentation system. Aeration had a weak repressing effect on the arginine deiminase pathway enzymes in cells growing on arginine as the only added substrate. By contrast, depending on the growth phase, a marked repression of the pathway by oxygen was observed in cells growing on glucose-arginine. We hypothesize that, in S. faecalis, the ATP pool is an important signal in the regulation of the arginine deiminase pathway. Mutants unable to utilize arginine as an energy source, isolated from the wild type, exhibited four distinct phenotypes. In group I the three enzymes of the arginine deiminase pathway were present and probably affected in the arginine uptake system. Group II mutants had no detectable arginine deiminase, whereas group III mutants had low levels of ornithine carbamoyltransferase. Group IV mutants were defective for all three enzymes of the pathway.