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-formylcarba moyl, and N-carbamoyl) and alpha-methyl analogues of aspartame (L-alph a-aspartyl-L-phenylalanine methyl ester; APM) to hydrolysis by human a nd porcine intestinal and kidney microvillar membranes and by purified preparations of the cell-surface peptidases aminopeptidase A (EC 3.4. 11.7) and amiqopeptidase W (EC 3.4.11.16) has been examined. Of the N- derivatized analogues of APM, only N-formylcarbamoyl-APM was hydrolyze d slightly by the human and porcine intestinal microvillar membrane pr eparations [1.1 nmol min(-1) (mg of protein)(-1) as compared to 80.1 n mol min(-1) mg of protein)(-1) for APM with the human jejunal microvil lar membranes]. However, the pattern of inhibition of the hydrolysis o f N-formylcarbamoyl-APM was distinct from that observed for APM; being inhibited (>80%) by actinonin or 1,10-phenanthroline but not by amast atin, bestatin; or rentiapril. In contrast to APM, N-formylcarbamoyl-A PM and the other N-derivatized analogues of APM were resistant to hydr olysis 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.