Temperature-jump studies on benzeneboronic acid-serine protease interactions. Subtilisin and alpha-chymotrypsin

The interactions of benzeneboronic acid (BBA) as a transition state analog with subtilisin (EC 3.4.21.4) and with alpha-chymotrypsin (EC 3.4.21.1) were investigated kinetically by the temperature-jump method using pH indicators. For both enzymes, the concentration dependence of the relaxation time was consistent with a two-step mechanism involving a fast bimolecular association followed by a slow, unimolecular process. The possibility of a trigonal-tetrahedral interconversion of BBA at the active site of the enzyme is discussed.