The deacylation of substituted benzoyl-α-chymotrypsins

Amshey, Joseph W.; Jindal, Satya P.; Bender, Myron L.

doi:10.1016/0003-9861(75)90310-0

Cited by 13 publications

(3 citation statements)

References 12 publications

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“…A possibility for gaining further insight into this question arises from the fact that the magnitudes of Hammett p values for acyl transfer reactions of acyl-substituted benzoate esters have been found to be highly sensitive to the charge on the attacking nucleophile (Caplow & Jencks, 1962; Williams & Salvador!, 1971; Hubbard & Kirsch, 1972). Indeed, the p values for the rates of deacylation of substituted benzoyl chymotrypsins are very close to those observed for alkaline hydrolysis (Caplow & Jencks, 1962;Williams & Salvador!, 1971; Wang & Shaw, 1972; Amshey et al, 1975;Kirsch et al, 1968; Kirsch, 1972). These observations support the conclusion that the net charge of the charge relay system is -1 in deacylation.…”

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confidence: 99%

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Effects of substituents on the rates of deacylation of substituted benzoyl papains. Role of a carboxylate residue in the catalytic mechanism

Zannis¹,

Kirsch²

1978

Biochemistry

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The effect of ring substituents on the rates of deacylation of 8 meta- and para-substituted benzoyl papains was evaluated. The rate constants were found to depend upon a single ionizing group of pKa = 4.2--4.3, and to decrease by a factor of approximately 2.2 when measured in 94% D2O/H2O. The rates of deacylation are increased greatly by electron-withdrawing groups on the benzene ring. The Hammett rho value is 2.74 +/- 0.32. A plot of the rate constants for deacylation of the benzoyl papains against the corresponding constants for substituted benzoyl chymotrypsins generates a straight line of slope 1.0. This result suggests a very similar distribution of charge on the benzoyl moiety in the transition state for the two enzymes, which is interpreted in terms of the net charge of the transition state for the deacylation of nonspecific acyl papains being equal to--1 with the general base catalyzed assistance to the attack of water on the acyl enzyme being provided by the negatively charged Asp-158 rather than by the neutral Asn-175-His-159 hydrogen bond network. This result together with a survey of literature data suggests that the role of Asp-158 in papain catalysis has been underestimated. The evidence advanced to date in support of the proposition that an imidazolium-159-cysteine-25 thiolate ion pair exists in native papain is evaluated and considered to be insufficient to decide the issue.

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confidence: 99%

“…Chymotrypsin data of: ( )Caplow & Jencks (1962); (0)Vishnu and Caplow (1969); (O)Wang and Shaw (1972); (0)Williams & Salvador! (1971); (V)Amshey et al (1975); (D)Bernhard et al (1966).…”

mentioning

confidence: 99%

Effects of substituents on the rates of deacylation of substituted benzoyl papains. Role of a carboxylate residue in the catalytic mechanism

Zannis¹,

Kirsch²

1978

Biochemistry

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“…A number of stable fluoro derivatives of serine-195 (Enriquez and Gerig, 1969;Gerig and Roe, 1974;Amshey et al, 1975;Gerig and McLeod, 1975;Amshey, 1976), a catalytically essential residue, and of methionine-192 (Bittner and Gerig, 1970a,b;Landis, 1976) have been reported. Table V compares the enzyme-induced chemical shifts in those derivatives that are available; in each case the enzyme-derived effects are referenced to the corresponding denatured enzyme or appropriate model compounds.…”

Section: Ix-chymotrypsinmentioning

confidence: 99%