L-ASPARAGINASE EC-2 FROM ESCHERICHIA COLI . SOME SUBSTRATE SPECIFICITY CHARACTERISTICS

L-Asparaginase EC-2 from Escherichia coli hydrolyzes L-glutamine and D-asparagine but at a much slower rate than L-asparagine. These amidase activities were not separated by several different methods of enzyme purification, by electrofocusing, nor by partial thermal inactivation. Upon injecting the enzyme into mice the activities in the blood plasma disappeared in accord with first-order kinetics with no change in the ratio of L-asparagine to D-asparagine or to L-glutamine hydrolysis. These data strongly suggest that the hydrolysis occurs at the same active site of the protein. Although product inhibition of L-asparagine hydrolysis occurred with ammonia at a pH value of 8.5, neither hydrolysis nor inhibition was found with L-aspartate, D-aspartate, L-glutamate, or D-glutamate. © 1969, American Chemical Society. All rights reserved.