The nature and reactivity of the 'essential' thiol in rabbit muscle creatine kinase III (EC 2.7.3.2)
| Autor: | Susan E. Hamilton, Paul Mackerras, Burt Zerner, Alison H. Fawcett, Aila I. Keto |
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| Rok vydání: | 1982 |
| Předmět: |
Macromolecular Substances
Biophysics Biochemistry Medicinal chemistry chemistry.chemical_compound Residue (chemistry) Reaction rate constant Mole Animals Molecular Biology Creatine Kinase chemistry.chemical_classification Binding Sites biology Muscles Sulfhydryl Reagents Cell Biology Phenylmercury Compounds Isoenzymes Chloromercurinitrophenols Kinetics Enzyme chemistry Iodoacetamide biology.protein Thiol Creatine kinase Rabbits Cysteine Protein Binding |
| Zdroj: | Biochemical and biophysical research communications. 107(1) |
| ISSN: | 0006-291X |
| Popis: | Rabbit muscle creatine kinase III (EC 2.7.3.2) can be reacted with 2-chloromercuri-4-nitrophenol and this results in the incorporation of two moles of mercurial per mole of enzyme subunit in a biphasic reaction. The second-order rate constant for the slow reaction is 475 ± 42 M-1 s-1. S-Carboxamidomethyl-creatine kinase reacts with a single mole of mercurial per mole of subunit. The rate constant, 466 ± 57 M-1 s-1, is almost identical to that for the slow reaction of the native enzyme. The reaction between 3-carboxy-4-nitrophenylthio-creatine kinase and 2-chloromercuri-4-nitrophenol has a second-order rate constant of 449 ± 56 M-1 s-1. The results may be explained if the mercurial reacts very rapidly with that cysteine residue which reacts independently with iodoacetamide or 5,5′-dithiobis(2-nitrobenzoic acid). However, 2-chloromercuri-4-nitrophenol also reacts more slowly with a second cysteine residue. Definition of the essentiality of thiol groups in enzymes by reaction with labile ligands, here represented by organomercurials, clearly must be approached with caution. |
| Databáze: | OpenAIRE |
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