Action of immobilized xanthine oxidase on purines
Braz. j. med. biol. res
; 28(3): 291-5, Mar. 1995. ilus, tab
Article
em En
| LILACS
| ID: lil-154693
Biblioteca responsável:
BR1.1
RESUMO
Xanthine oxidase was covalently immbolized on polyacrylamide gel beads, polyamide- 11 and dacron. Hypoxanthine (15 ml of 200 µM), prepared in 0.1 M phosphate buffer, pH 8.0, was circulated through a column containing 1.0g derivatized enzyme at a flow rate of 1.0 ml/min at 28§C. Specific activities of 0.660, 0.072 and 0.016 Units/mg of protein were demonstrable for the polyacrylamide gel beads, dacron and polyamide-11 derivatives, respectively. The action of these water insoluble enzyme derivatives on 6 mercaptopurine (15 ml of 660 µM) was also investigated, under the same experimental conditions, showing specific activites of 0.063 Units/mg, 0.574 µUnits/mg and 0.118 µUnitis/mg, respectively. The 6-mercaptopurine oxidative pathway catalyzed by immobilized xanthine oxidase on dacron stopped at the intermediate compound 6-mercaptopurine oxidative on dracon stopped at the intermediate compound, 6-mercapto-8-hydroxypurine, so that no 6-thiouric acid was produced, whereas the immobilized preparations using polyacrylamide gel beads and polyamide-11 behaved like the soluble enzyme, namely, 6-thiouric acid was the final product. The behavior of dracon-xanthine oxidase immobilized on these three supports was similar to the soluble enzyme. However, although its oxidation is stoichiometric for polyacrylamide gel beads and polyamide- 11 derivatives, and no xanthine formation is observed (steady-state equilibrium), under the action of the enzymedacron derivative the xanthine formation rate (0.164 µUnits/mg) is higher than the uric acid formation rate (0.017 µUnits/mg) compared to the hypoxanthine consumption (0.072 µUnits/mg). These findings suggest again that xanthine oxidase-dacron derivative is limited to the catalysis of oxidation of hypoxanthine carbon atom number 2 as in 6-mercaptopurine
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Coleções:
01-internacional
Base de dados:
LILACS
Assunto principal:
Xantina Oxidase
/
Enzimas Imobilizadas
/
Mercaptopurina
Idioma:
En
Revista:
Braz. j. med. biol. res
Assunto da revista:
BIOLOGIA
/
MEDICINA
Ano de publicação:
1995
Tipo de documento:
Article
País de publicação:
Brasil