Stability of N-Derivatized and .alpha.-Methyl Analogs of Aspartame to Hydrolysis by Mammalian Cell-Surface Peptidases

The biological stability of the N-derivatized (N-formyl, N-formylcarbamoyl, and N-carbamoyl) and alpha-methyl analogues of aspartame (L-alpha-aspartyl-L-phenylalanine methyl ester; APM) to hydrolysis by human and porcine intestinal and kidney microvillar membranes and by purified preparations of the cell-surface peptidases aminopeptidase A (EC 3.4.11.7) and aminopeptidase W (EC 3.4.11.16) has been examined. Of the N-derivatized analogues of APM, only N-formylcarbamoyl-APM was hydrolyzed slightly by the human and porcine intestinal microvillar membrane preparations [1.1 mmol min(-1) (mg of protein)(-1) as compared to 80.1 nmol min(-1) (mg of protein)(-1) for APM with the human jejunal microvillar membranes]. However, the pattern of inhibition of the hydrolysis of N-formylcarbamoyl-APM was distinct from that observed for APM, being inhibited ( 80%) by actinonin or 1,10-phenanthroline but not by amastatin, bestatin, or rentiapril. In contrast to APM, N-formylcarbamoyl-APM and the other N-derivatized analogues of APM were resistant to hydrolysis by aminopeptidases A and W. All of the alpha-methyl derivatives of APM were resistant to hydrolysis by both the microvillar membrane preparations and the purified peptidases