METHYL AND PHENYL-ESTERS AND THIOESTERS OF CARBOXYLIC-ACIDS AS SURROGATE SUBSTRATES FOR MICROASSAY OF PROTEINASE-K ESTERASE-ACTIVITY

The development of a microassay for proteinase K esterase activity wit h carboxylic acid eaters is reported using novel substrates of the gen eral formula R-C(O)-XR'. Highest rates of hydrolysis have been obtaine d with the O-phenyl esters CH3(CH2)(n=1-2)-S-(CH2)(n=1-2)C(O)-O-phenyl and their thioester analogs in studies where R, X and R' have been va ried. The phenol release has been measured with 4-aminoantipyrine and potassium ferricyanide to determine the rates of O-phenyl ester hydrol yses. Thioester hydrolyses have been monitored continuously with 5,5'- dithio-bis (2-nitrobenzoic acid).