A mechanistic study of purple acid phosphatases

Purple acid phosphatases (PAPs) are known as monoesterases; however, kinetic studies performed on pig and red kidney bean PAP with diester substrates reveal that the enzyme has diesterase activity which diminishes as the size of the secondary ester increases. Experiments reveal that the enzyme hydrolyzes diesters and then monoesters processively, providing evidence for a two-step binding motif.; Kinetic isotope effects measured for PAPs from pig and kidney bean that use p-nitrophenyl phosphate and m-nitrobenzyl phosphate as substrates also suggest a two-step binding mechanism in which the phosphate substrate binds monodentately first, then bidentately with possible deprotonation of the substrate occurring during catalysis.