Characterization and Partial Purification of Aldose-6-phosphate Reductase (Alditol-6-Phosphate:NADP 1-Oxidoreductase) from Apple Leaves 12
AUTOR(ES)
Negm, Fayek B.
RESUMO
Aldose-6-phosphate reductase (alditol 6-phosphate:NADP 1-oxidoreductase) was isolated and characterized from mature apple leaves (Malus domestica cv. Starkrimson). The enzyme was purified 79-fold. The enzyme catalyzed the following reversible reaction: d-glucose 6-phosphate + NADPH + H+ ⇄ d-sorbitol 6-phosphate + NADP+. No activity was detected when NAD+ was substituted for NADP+ or when NADH was substituted for NADPH. The enzyme reduced d-galactose 6-phosphate at a higher rate than d-glucose 6-phosphate. d-Mannose 6-phosphate and 2-deoxy-d-glucose 6-phosphate were reduced at low rates. d-Glucose 1-phosphate, d-fructose 6-phosphate, d-ribose 5-phosphate, d-glucose, and sorbitol did not serve as substrates. The pH optimum for both d-sorbitol 6-phosphate oxidation and d-glucose 6-phosphate reduction was 9.5. The Km values for d-sorbitol 6-phosphate oxidation and d-glucose 6-phosphate reduction were 3.9 and 20 millimolar, respectively. AgNO3 (0.1 millimolar) and p-chloromercuribenzoate (1.0 millimolar) completely inhibited the enzyme.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=425637Documentos Relacionados
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