Bacterial metabolism of arginine

Cellular suspensions of Streptococcus lactis metabolize arginine to ornithine, carbon dioxide and ammonia. Neither urea nor citrulline is attacked;Dialyzed cell-free extracts degrade arginine to equimolar quantities of citrulline and ammonia. The optimum pH range for the reaction is pH 5.4--5.8. The reaction is inhibited by arsenite; hydrozylamine, semicarbazide, iodo-acetate and azide are without effect. The extracts are highly specific for arginine and are useful for the quantitative degradation of the guanido group of arginine in the presence of guanido and carbamido compounds and amino acids;Dialyzed cell-free extracts metabolize citrulline to equimolar amounts of ornithine, carbon dioxide and ammonia when supplemented with orthophosphate, Mg++ and adenosine diphosphate. Arsenate readily replaces orthophosphate; neither Mg++ nor adenosine diphosphate is then required. The pH optimum for the reaction, either in phosphate or arsenate, is pH 6.2--6.3. The reaction is inhibited by D-citrulline, L-ornithine and fluoride in the presence of phosphate or arsenate. Orthophosphate is inhibitory in the presence of arsenate;Decrease in orthophosphate concentration occurs during the conversion of citrulline to ornithine. The phosphate ester formed is hydrolyzed in 1 N hydrochloric acid at 100°C in 10 minutes. Upon addition of glucose and hexokinase to the test system, orthophosphate disappears but no acid-labile ester can be detected. A complete chemical balance of products shows that for each mole of citrulline degraded one mole of orthophosphate is required and one mole of adenosine triphosphate is formed. The ratio NH3 (or CO2):P is nearly one and remains constant with time;The reversibility of the citrulline phosphorylase reaction has been demonstrated by use of C14O2 in exchange type of experiments. A small net synthesis of citrulline has also been noted. Adenosine triphosphate is required for fixation of C14O2;A mechanism for the bacterial degradation and synthesis of citrulline is proposed