Properties of Histidine Decarboxylase from Rat Gastric Mucosa
| Autor: | Alain Savany, L. Cronenberger |
|---|---|
| Rok vydání: | 2005 |
| Předmět: |
Male
Hot Temperature Chemical Phenomena Carboxy-Lyases Reducing agent Histidine Decarboxylase Biochemistry Cofactor chemistry.chemical_compound Non-competitive inhibition Animals Pyridoxal phosphate chemistry.chemical_classification Chromatography biology Tryptophan Rats Inbred Strains Hydrogen-Ion Concentration Histidine decarboxylase Enzyme assay Rats Chemistry Enzyme chemistry Gastric Mucosa Pyridoxal Phosphate biology.protein |
| Zdroj: | European Journal of Biochemistry. 123:593-599 |
| ISSN: | 1432-1033 0014-2956 |
| DOI: | 10.1111/j.1432-1033.1982.tb06574.x |
| Popis: | The properties of specific histidine decarboxylase from highly purified rat gastric mucosa preparations were studied. The kinetic parameters were pH dependent: the apparent Km value varied inversely with pH; the maximum reaction velocity was reached at pH 6.6; the optimum pH was related to substrate concentration. The enzyme was unstable below pH 5.5. The effect of temperature was investigated and the enzyme activity was optimum near 56 degrees C. The thermal inactivation of the enzyme showed the presence of several active forms displaying distinct thermostabilities. The effect of coenzyme and substrate on heat stability was established. A small amount of pyridoxal phosphate was required for maximum enzyme activity, and the Km was low. The cofactor appeared to be tightly bound to the apoenzyme; nevertheless there was a fraction more easily resolved by dialysis. With high pyridoxal phosphate concentrations non-competitive inhibition occurred. Histamine inhibited the enzyme at high concentrations, the inhibition being competitive with respect to the substrate. No metal ion was required for enzyme activity; the enzyme was inhibited by sulfhydryl reagents and heavy metal ions, and also by high concentrations of reducing agents. The tryptophan residue of the holoenzyme seemed to be essential for the catalytic process. |
| Databáze: | OpenAIRE |
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