title: Purification and partial characterization of an aldo-keto reductase from Saccharomyces cerevisiae.
abstract: A cytosolic aldo-keto reductase was purified from Saccharomyces cerevisiae ATCC 26602 to homogeneity by affinity chromatography, chromatofocusing, and hydroxylapatite chromatography. The relative molecular weights of the aldo-keto reductase as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and size exclusion chromatography were 36,800 and 35,000, respectively, indicating that the enzyme is monomeric. Amino acid composition and N-terminal sequence analysis revealed that the enzyme is closely related to the aldose reductases of xylose-fermenting yeasts and mammalian tissues. The enzyme was apparently immunologically unrelated to the aldose reductases of other xylose-fermenting yeasts. The aldo-keto reductase is NADPH specific and catalyzes the reduction of a variety of aldehydes. The best substrate for the enzyme is the aromatic aldehyde p-nitrobenzaldehyde (Km = 46 microM; kcat/Km = 52,100 s-1 M-1), whereas among the aldoses, DL-glyceraldehyde was the preferred substrate (Km = 1.44 mM; kcat/Km = 1,790 s-1 M-1). The enzyme failed to catalyze the reduction of menadione and p-benzoquinone, substrates for carbonyl reductase. The enzyme was inhibited only slightly by 2 mM sodium valproate and was activated by pyridoxal 5'-phosphate. The optimum pH of the enzyme is 5. These data indicate that the S. cerevisiae aldo-keto reductase is a monomeric NADPH-specific reductase with strong similarities to the aldose reductases.
authors.affiliation: Department of Microbiology and Biochemistry, University of the Orange Free State, Bloemfontein, South Africa.
authors.forename: A
authors.initials: A
authors.lastname: Kuhn
authors.forename: C
authors.initials: C
authors.lastname: van Zyl
authors.forename: A
authors.initials: A
authors.lastname: van Tonder
authors.forename: B A
authors.initials: BA
authors.lastname: Prior
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D000449:Aldehyde Reductase; D000074408:Aldo-Keto Reductases; D000595:Amino Acid Sequence; D000818:Animals; D006801:Humans; D007120:Immunochemistry; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D000429:Alcohol Oxidoreductases; D000074408:Aldo-Keto Reductases; D000449:Aldehyde Reductase