The effect of methanol and dioxan on the rates of the β-galactosidase-catalysed hydrolyses of some β-d -galactopyranosides: rate-limiting degalactosylation. The pH-dependence of galactosylation and degalactosylation
| Autor: | Michael L. Sinnott, Odile M. Viratelle |
|---|---|
| Rok vydání: | 1973 |
| Předmět: |
Chemical Phenomena
Protonation Buffers Dioxins Biochemistry Medicinal chemistry Nitrophenols Hydrolysis chemistry.chemical_compound Ph dependence Organic chemistry Enzyme kinetics Molecular Biology chemistry.chemical_classification Binding Sites Methanol Cell Biology Limiting Hydrogen-Ion Concentration Galactosidases Rate of increase Chemistry Kinetics Enzyme chemistry Enzymology Dinitrophenols Mathematics Protein Binding |
| Zdroj: | Biochemical Journal. 133:81-87 |
| ISSN: | 0264-6021 |
| DOI: | 10.1042/bj1330081 |
| Popis: | 1. The effect of methanol on the β-galactosidase-catalysed hydrolysis of some nitrophenyl β-d-galactopyranosides has been studied under steady-state conditions. 2. The initial fractional rate of increase of kcat. as a function of methanol concentration with 2,4- and 3,5-dinitrophenyl β-d-galactopyranosides, but not with the other substrates studied, indicated that degalactosylation of the enzyme was rate-limiting. 3. The decrease in kcat. at high methanol concentrations for these substrates is considered to arise from causes other than galactosylation becoming rate-limiting. 4. Both galactosylation and degalactosylation of the enzyme require protonation of a group of pKa approx. 9. |
| Databáze: | OpenAIRE |
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