Regulatory effects of substrates on a phosphotransferase from Aerobacter aerogenes and modification of its activity by partial proteolysis.

An enzyme isolated from Aerobacter aerogenes acts both as phosphomonoesterase and phosphotransferase with glucose, glucosides, glucosamine, and N-acetyl glucosamine as acceptors. When glucose-6-phosphate is the phosphate donor, these acceptors appear to act as activators of the enzyme, while with p-nitrophenyl phosphate, alpha-glycerophosphate, fructose-1,6-diphosphate, and several other phosphate esters as donors, the same acceptors act as noncompetitive inhibitors. With p-nitrophenyl phosphate as the phosphate donor, no inhibition is observed when glucose is replaced as acceptor by 2-deoxy glucose. The inhibition by glucose and other acceptors is eliminated at low pH or by increasing the temperature of reaction. Partial proteolysis of the enzyme by chymotrypsin produces a modified enzyme (gl-phosphotransferase-Ch) that shows altered relative velocities for the hydrolysis of several substrates as well as altered regulatory effects by acceptors.