A Versatile Mechanistic Probe for Three EnzymesIn an earlier publication (la) we described an experiment involving the enzymatically catalyzed hydrolysis of p-nitrophenyl acetate (PNPA) by bovine carbonic anhydrase II (BCA).Since that time, many student projects have been derived from these experiments at Seattle University and the University of Washington. They have allowed this part of our biochemistry laboratory activities to be expanded to include enzyme assays for two additional enzymes that also exhibit esterase activity. The reaction of eq 1 is versatile: It is catalyzed not only by carbonic anhydrase but also by a-chymotrypsin (a-CT) and acetylcholinesterase (AcCE). Thus, a single reaction, conveniently monitored, serves as a pedagogic tool and a mechanistic probe for