A lecture by Kevin Ahern of Oregon State University to his BB 450/550 class. Topics covered include catalysis, mechanism, chymotrypsin, serene proteases, DIPF, suicide inhibition, alkoxide ion, oxyanion hole, S1 pocket, nucleophile, slow, fast. Highlights Enzymes IV 1.Chemicals, such as DIPF and iodoacetate, covalently (and irreversibly) bind to the side chains of specific amino acids (serine and cysteine, respectively) and if these side chains are essential for the catalytic action of the enzyme, the enzyme will not catalyze reactions after being treated with these chemicals. 2. Penicillin is a substance that resembles the substrate of an enzyme in bacteria that helps make the bacterial cell wall. When it binds to the enzyme, it inactivates the enzyme by covalently bonding to the active site, thus destroying the enzyme (and killing the bacterium containing it). An inhibitor of this type is known as a suicide inhibitor. Highlights Catalytic Mechanisms 1. Proteases catalyze the hydrolysis of peptide bonds in polypeptides. They are usually fairly specific for certain amino acids and cut at or near those amino acids. 2. Chymotrypsin is a protease whose activity has been closely studied. Conveniently, the activity of chymotrypsin can be studied using an artificial substrate which, when cleaved by the enzyme, releases a yellow product. 3. When the release of the colored substrate by the enzyme is studied, it appears to occur in two different rates. First there is a VERY rapid ...
