Studies on Kojic Acid Metabolism by Microorganisms

Part XI. Comenic Aldehyde Dehydrogenase (5-Methoxy Comenic Aldehyde Dehydrogenase)

抄録

An enzyme, comenic aldehyde dehydrogenase, which catalyzes the oxidation of comenic aldehyde to comenic acid was partially purified from cell extract of Arthrobacter ureafaciens K-1.
The enzyme was purified 31-fold at Sephadex G-100 filtration step, 112-fold at DEAE-Sephadex A-50 fractionation step, and recovery of the activity was 73.30% and 38.5%, respectively.
NADP and magnesium ion were essential for the oxidation. The enzyme shows optimum activity at pH 7.8. Enzyme activity was extremely sensitive to sulfhydryl reagents such as p-chloromercuribenzoate and monoiodoacetate. L-Cysteine or dithiothreitol protected the enzyme from p-chtoromercuribenzoate inhibition. Carbonyl reagents, such as hydroxylamine and semicarbazide, inhibit the enzyme reaction by formation of addition compounds between carbonyl reagents and aldehyde group of the substrate. The enzyme was completely inactivated after heating for 5 min at 40°C. The Km for 5-methoxy comenic aldehyde is 2.5×10^-6 M, and for NADP is 0.4×10^-6 M. The reaction product, 5-methoxy comenic acid was identified by paperchromatography. The characterization of the enzyme has been carried out by using 5-methoxy comenic aldehyde as the substrate in stead of comenic aldehyde.