Literature DB >> 27512

Dependence of the catalytic activity of papain on the ionization of two acidic groups.

S D Lewis, F A Johnson, A K Ohno, J A Shafer.   

Abstract

The pH dependence of kcat/Km for the papain-catalyzed hydrolysis of ethyl hippurate, N-alpha-benzoyl-L-citrulline methyl ester, and the p-nitroanilide, amide, and ethyl ester derivatives of N-alpha-benzoyl-L-arginine was determined below pH 6.4. The value of kcat/Km was observed to be modulated by two acid ionizations rather than a single ionization as previously believed. For the five substrates studied, the average pK values for the two ionizations are 3.78 +/- 0.2 and 3.95 +/- 0.1 at T/2 0.3, 25 degrees C. The observation that similar pK values were obtained with different substrates was taken as evidence that the kinetically determined pK values are close in value to true macroscopic ionization constants for ionization of groups on the free enzyme.

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Year:  1978        PMID： 27512

Source DB:  PubMed          Journal:  J Biol Chem        ISSN： 0021-9258            Impact factor:   5.157


  8 in total

1.  Differences in the chemical and catalytic characteristics of two crystallographically 'identical' enzyme catalytic sites. Characterization of actinidin and papain by a combination of pH-dependent substrate catalysis kinetics and reactivity probe studies targeted on the catalytic-site thiol group and its immediate microenvironment.

Authors:  E Salih; J P Malthouse; D Kowlessur; M Jarvis; M O'Driscoll; K Brocklehurst
Journal:  Biochem J       Date:  1987-10-01       Impact factor: 3.857

2.  The interplay of electrostatic fields and binding interactions determining catalytic-site reactivity in actinidin. A possible origin of differences in the behaviour of actinidin and papain.

Authors:  D Kowlessur; M O'Driscoll; C M Topham; W Templeton; E W Thomas; K Brocklehurst
Journal:  Biochem J       Date:  1989-04-15       Impact factor: 3.857

3.  Identification of signalling and non-signalling binding contributions to enzyme reactivity. Alternative combinations of binding interactions provide for change in transition-state geometry in reactions of papain.

Authors:  D Kowlessur; C M Topham; E W Thomas; M O'Driscoll; W Templeton; K Brocklehurst
Journal:  Biochem J       Date:  1989-03-15       Impact factor: 3.857

4.  Clarification of the pH-dependent kinetic behaviour of papain by using reactivity probes and analysis of alkylation and catalysed acylation reactions in terms of multihydronic state models: implications for electrostatics calculations and interpretation of the consequences of site-specific mutations such as Asp-158-Asn and Asp-158-Glu.

Authors:  G W Mellor; M Patel; E W Thomas; K Brocklehurst
Journal:  Biochem J       Date:  1993-08-15       Impact factor: 3.857

Review 5.  Current problems in mechanistic studies of serine and cysteine proteinases.

Authors:  L Polgár; P Halász
Journal:  Biochem J       Date:  1982-10-01       Impact factor: 3.857

6.  Purification and characterization of a digestive cysteine proteinase from the American lobster (Homarus americanus).

Authors:  M V Laycock; T Hirama; S Hasnain; D Watson; A C Storer
Journal:  Biochem J       Date:  1989-10-15       Impact factor: 3.857

7.  Ionization characteristics of the Cys-25/His-159 interactive system and of the modulatory group of papain: resolution of ambiguity by electronic perturbation of the quasi-2-mercaptopyridine leaving group in a new pyrimidyl disulphide reactivity probe.

Authors:  G W Mellor; E W Thomas; C M Topham; K Brocklehurst
Journal:  Biochem J       Date:  1993-02-15       Impact factor: 3.857

8.  Chemical evidence for the pH-dependent control of ion-pair geometry in cathepsin B. Benzofuroxan as a reactivity probe sensitive to differences in the mutual disposition of the thiolate and imidazolium components of cysteine proteinase catalytic sites.

Authors:  F Willenbrock; K Brocklehurst
Journal:  Biochem J       Date:  1986-08-15       Impact factor: 3.857
  8 in total

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