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Br-C(l)-C(2) 109.0 0.5 C(l)-C(2) 1.509 0.010 C(l)-C(2)-C(3) 120.3 0.7 C(2)-C(3) 1.474 0.011 C(l)-C(2)-N 112.5 0.7 C(2)-N 1.291 0.010 N-C(2)-C(3) 127.2 0.6 N-O 1.409 0.008 C(2)-N-D 113.5 0.7 C(3)-C(4) 1.404 0.010 C(2)-C(3)-C(4) 119.3 0.7 C(4)-C(5) 1.366 0.015 C(2)-C(3)-C(8) 122.1 0.6 C(5)-C(6) 1.358 0.015 C(4)-C(3)-C(8) 118.6 0.7 C(6)-C(7) 1.389 0.015 C(3)-C(4)-C(5) 120.5 0.8 C(7)-C(8) 1.385 0.014 C(4)-C(5)-C(6) 121.0 0.9 C(8)-C(3) 1.402 0.011 0.2919(9) 0.9511 (8) 0.3123 (8) C(ll) 0.3358(7) 0.9864 (7) 0.4120(8)from the National Science Foundation (J.

No abstract

The a-Chymotrypsin-Catalyzed Hydrolysis of Lactones1 Sir:«-Chymotrypsin, a pancreatic protease and esterase, was recently shown to react rapidly and stoichiometrically with aromatic five-membered sultones.2 The

Reaction of 2-hydroxy-5-nitro-a-toluenesulfonic acid sultone with serine-195 at the active site of achymotrypsin produces a sulfonyl enzyme which undergoes desulfonylation under conditions where a-toluenesulfonyl-a-chymotrypsin is stable. The rate of desulfonylation of 2-hydroxy-5-nitro-a-toluenesulfonyl-a-chymotrypsin (II) has been measured using a large excess of the specific substrate V-acetyl-L-tryptophan methyl ester which rapidly scavenges any free enzyme. One pathway for desulfonylation involves attack of the phenolic hydroxyl group in II on the sulfonyl function to regenerate the starting sultone. This reaction appears to involve the catalytic participation of the active-site residue histidine-57 and is among the first examples where a reactive function introduced into an enzyme molecule has been shown to act as an intramolecular nucleophile.We have shown that 2-hydroxy-5-nitro-a-toluenesulfonic acid sultone (I) reacts rapidly and stoichiometrically with the active site of the proteolytic enzyme -chymotrypsin (CT) to produce a catalytically inactive sulfonyl enzyme II.3 This sulfonyl enzyme then decomposes in a much slower first-order reaction to produce 2-hydroxy-5-nitro-a-toluenesulfonic acid (III). These observations have been interpreted in terms of the reaction sequence shown in eq 1 which is similar to that postulated to hold for normal ester or amide substrates.4 In eq 1 E represents the enzyme, S is the sultone, ES is a noncovalent complex of the two species, ES' is the covalent sulfonyl enzyme intermediate, P is the product acid III, and Ks is the dissociation constant for the ES complex.surements of the kinetics of the production of III we (5) P.