Prediction of the structure and function of AstA and AstB, the first two enzymes of the arginine succinyltransferase pathway of arginine catabolism.

Arginine succinyltransferase and succinylarginine dihydrolase catalyze the first two steps of arginine catabolism by the arginine succinyltransferase pathway. This route is the only major arginine catabolic pathway in Escherichia coli including its pathogenic strains O157 and CFT073. We have used fold recognition tools and identified novel homologies between each of these two enzymes and proteins of known three-dimensional structure: arginine succinyltransferase belongs to the acyl-CoA N-acyltransferase superfamily and succinylarginine dihydrolase belongs to the amidinotransferase superfamily. These findings shed light on the structures, catalytic mechanisms and evolution of diverse enzymes involved in arginine catabolism.