The inhibition of chymotrypsin by diethyl p-nitrophenyl phosphate

Abstract

The alkyl fluorophosphonates were first shown in 1940 (Adrian, Feldberg & Kilby, 1947) to be very powerful inhibitors of cholinesterase, and for a time they were thought to be quite specific for this enzyme. Later, other esterases, such as human milk lipase and liver esterase (Webb, 1948) and citrus acetylesterase (Jansen, Nutting & Balls, 1947) were * The non-protein nitrogen was less than 0-1 %.

The reaction of p-nitrophenyl esters with chymotrypsin and insulin

“…Both had been recrystallized from MgSO4 solutions. The percentage purities, calculated as in a previous paper (Hartley & Kilby, 1952) from the specific proteolytic activities were 65 and 48 % for samples B and C, respectively.…”

“…These were measured by methods described by Hartley & Kilby (1952 centrifuge tubes. The solutions were cooled, and 2 ml.…”

“…This compound is a member of a group of organophosphorus insecticides which are powerful inhibitors of cholinesterases. They will also inhibit chymotrypsin, and it has been shown that this inhibition is due to combination of the compounds with a single active centre in the enzyme Hartley & Kilby, 1952). We investigated the reaction ofchymotrypsin with certain structural analogues of E 600, namely p-nitrophenyl ethyl carbonate (NPC) p-NO2.C,H4.…”

Theory of the Transient Phase in an Enzyme System Involving Two Enzyme-Substrate Complexes: The Case of the Formation of Products From the First Complex

“…Inserting the value of y1 illto equation [3] and integrating one obtains for the value of $1 as a function of time When t is sufficiently large, so that the terins eF' and eG' become negligible (Fantl G are always negative), I t is evident that equation [19] is the proper integrated form-of equation [5] for an open system in which so is maintained constant.…”

“…In certain cases, such as the hydrolysis of esters by chymotrypsin (3) or by trypsi11 (4), there are indications that the release of products involves two steps, one for the release of the alcohol and one for the release of the acid. Follo\ving the rate of appearance of the first-appearing product is often possible (if the alcohol is a phenol, for example, and can be determined calorimetrically), and could provide additional useful information on the mechanism of the reaction.…”