PEPSIN-CATALYZED HYDROLYSIS OF BIS-P-NITROPHENYL SULFITE AND ITS INHIBITION BY DIPHENYL SULFITE AT PH-2

Bis-p-nitrophenyl sulfite, BNPS, is an excellent substrate for the proteolytic enzyme pepsin at pH 2. The enzyme-catalyzed hydrolysis of this sulfite proceeds approximately 103 times faster than that of other known sulfite esters. This rate acceleration is apparently due principally to the high value of kest, the catalytic rate constant, for the enzymatic hydrolysis of BNPS. The Michaelis constant for the pepsin-catalyzed hydrolysis of the nitro-substituted aromatic sulfite ester is not very different from that which is observed in the case of the unsubstituted ester diphenyl sulfite, DPS. We have studied the inhibition of the enzymatic hydrolysis of BNPS by added DPS. The inhibition constant, K1, which we have measured in this way for DPS differs appreciably from the Michaelis constant we have found for the pepsin-catalyzed hydrolysis of DPS. © 1969, American Chemical Society. All rights reserved.