REGULATORY EFFECTS OF SUBSTRATES ON A PHOSPHOTRANSFERASE FROM Aerobacter aerogenes AND THE MODIFICATION OF ITS ACTIVITY BY PARTIAL PROTEOLYSIS*
Abstract
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, α-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.
Footnotes
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↵ † Present address: New York University College of Medicine, Department of Medicine, Department of Medicine, Irvington House.
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↵ * Supported by USPHS grant AI 07796 from the National Institute of Allergy and Infectious Diseases and grant GB 5946 from the National Science Foundation. We are indebted to Dr. R. Warner for the analytical ultracentrifugations and to J. Schaeffer for expert technical assistance.
