Hydrolysis of organophosphate triesters by Escherichia coli aminopeptidase P

Aminopeptidase P (AMPP, EC 3.4.11.9) from Escherichia coli catalyzes the cleavage of amino-terminal X-Pro peptide bonds. In this study, AMPP was found to catalyze the hydrolysis of a wide range of organophosphate triesters (1–7). The activity of AMPP was promoted in the presence of Mn2+, and slight activation was achieved by treatment with Cd2+. The enzymatic rates of hydrolysis for organophosphate triesters (3 and 5) with both isopropyl (or isobutyl) and methyl substituents attached to the phosphorus atom were from 5- to 36-fold higher compared to the corresponding analogs (4 and 6, 7). Three mutants, R153W, R153L and R370L, have been characterized and exhibited from 1.2- to 1.5-fold increases in hydrolyzing 1–7 compared to the wild-type enzyme. These results demonstrate that there is a flanking hydrophobic interaction between the substituent group of substrates and position 153 or 370 in AMPP to facilitate the hydrolysis of organophosphate triesters.