Functional micellar catalysis. Part 4. Catalysis of activated ester hydrolysis by surfactant systems as chymotrypsin models

Abstract

Micelles made up of each of five surfactants of general structure C₁₆H₃₃N(CH₃)₂(CH₂)_nFH [(I), n= 2, FH = OH; (II), n= 1, FH = C(Ph)NOH; (III), n= 1, FH = CO·C(Ph)NOH;(IV), n= 1, FH = imidazol-4-yl (lm); (V), n= 2, FH = NH·CO·lm], of the bifunctional surfactant C₁₆H₃₃N(CH₃)(CH₂lm)(CH₂CH₂OH)(VI), of N^α-myristoylhistidine (VII), and of N-methylmyristohydroxamic acid (VIII) have been investigated as catalysts of p-nitrophenyl acetate (PNPA) and hexanoate (PNPH) hydrolysis in the pH range 7–8. The activity of α-chymotrypsine toward PNPA at pH 7.95 has also been measured. The kinetic analysis was carried out under the same conditions in each instance and rate data are directly compared. A nucleophilic mode of action is indicated for each type of micelle and differences in the rate of acylation and turnover are discussed with reference to related micellar systems and to the enzyme α-chymotrypsin.