The preparation of a new stable and active form of chymotrypsin is described. The enzyme possesses the threonine 147 instead of alanine 149 as the NH2 terminal group of the C chain and has been called α1 chymotrypsin. The conformational transition that affects chymotrypsins at alkaline pH was investigated and compared with that of α- and δ chymotrypsins by studying the kinetic constants and their pH dependencies for the hydrolysis of various specific ester substrates. The k(cat) values obtained with α1 chymotrypsin are similar to those of α- and δ chymotrypsins. The K(m) values showed a progressive increase toward the alkaline pH region. The shape of the K(m) pH profiles closely resemble those of δ chymotrypsin and differ considerably from the behavior of α chymotrypsin. The results strongly implicate the participation of the alanine 149 amino group in the reversible inactivation of α chymotrypsin at high pH.
|Number of pages||6|
|Journal||Journal of Biological Chemistry|
|Publication status||Published - 1973|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology