Merck
CN

Ketose reductase activity in developing maize endosperm.

Plant physiology (1987-07-01)
D C Doehlert
摘要

Ketose reductase (NAD-dependent polyol dehydrogenase EC 1.1.1.14) activity, which catalyzes the NADH-dependent reduction of fructose to sorbitol (d-glucitol), was detected in developing maize (Zea mays L.) endosperm, purified 104-fold from this tissue, and partially characterized. Product analysis by high performance liquid chromatography confirmed that the enzyme-catalyzed reaction was freely reversible. In maize endosperm, 15 days after pollination, ketose reductase activity was of the same order of magnitude as sucrose synthase activity, which produces fructose during sucrose degradation. Other enzymes of hexose metabolism detected in maize endosperm were present in activities of only 1 to 3% of the sucrose synthase activity. CaCl(2), MgCl(2), and MnCl(2) stimulated ketose reductase activity 7-, 6-, and 2-fold, respectively, but had little effect on NAD-dependent polyol dehydrogenation (the reverse reaction). The pH optimums for ketose reductase and polyol dehydrogenase reactions were 6.0 and 9.0, respectively. K(m) values were 136 millimolar fructose and 8.4 millimolar sorbitol. The molecular mass of ketose reductase was estimated to be 78 kilodaltons by gel filtration. It is postulated that ketose reductase may function to metabolize some of the fructose produced during sucrose degradation in maize endosperm, but the metabolic fate of sorbitol produced by this reaction is not known.

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Sigma-Aldrich
葡萄糖-6-磷酸脱氢酶 来源于面包酵母(酿酒酵母), Type XV, lyophilized powder, 200-400 units/mg protein (modified Warburg-Christian)
Sigma-Aldrich
葡萄糖-6-磷酸脱氢酶 来源于面包酵母(酿酒酵母), Type VII, ammonium sulfate suspension, ≥200 units/mg protein
Sigma-Aldrich
葡萄糖-6-磷酸脱氢酶 来源于肠系膜明串珠菌, recombinant, expressed in E. coli, ammonium sulfate suspension, ≥550 units/mg protein (biuret)
Sigma-Aldrich
葡萄糖-6-磷酸脱氢酶 来源于面包酵母(酿酒酵母), Type IX, lyophilized powder, 200-400 units/mg protein (modified Warburg-Christian)