title: Mild detergent treatment of Candida tropicalis reveals a NADPH-dependent reductase in the crude membrane fraction, which enables the production of pure bicyclic exo-alcohol.
abstract: This study demonstrated the occurrence of a NADPH-dependent exo-alcohol reductase in the crude membrane fraction of Candida tropicalis. Cytosolic endo-alcohol reductase activity could be separated from the membrane-bound exo-alcohol activity by means of detergent treatment, enabling the preparation of pure exo-alcohol via the enzymatic conversion of the bicyclic diketone, bicyclo[2.2.2]octane-2,6-dione. The exo-alcohol reductase is, to our knowledge, the first membrane-bound NADPH-dependent reductase accepting a xenobiotic carbonyl substrate that was not a steroid. When C. tropicalis was grown on D-sorbitol, a two-fold increase in the exo-reductase activity was observed as compared to when grown on glucose. An in silico comparison at the protein level between putative xenobiotic carbonyl reductases in Candida albicans, C. tropicalis and Saccharomyces cerevisiae was performed to explain why Candida species are often encountered when screening yeasts for novel stereoselective reduction properties. C. albicans contained more reductases with the potential to reduce xenobiotic carbonyl compounds than did S. cerevisiae. C. tropicalis had many membrane-bound reductases (predicted with the bioinformatics program, TMHMM), some of which had no counterpart in the two other organisms. The exo-reductase is suspected to be either a beta-hydroxysteroid dehydrogenase or a polyol dehydrogenase from either the short chain dehydrogenase family or the dihydroflavonol reductase family.
authors.affiliation: Department of Applied Microbiology, Lund University, PO Box 124, 221 00 Lund, Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Katz
authors.forename: Ted
authors.initials: T
authors.lastname: Johanson
authors.forename: Marie-F
authors.initials: MF
authors.lastname: Gorwa-Grauslund
mesh_terms: D000429:Alcohol Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism; D000438:Alcohols / Q000378:metabolism; D001643:Bridged Bicyclo Compounds / Q000378:metabolism; D041022:Candida tropicalis / Q000201:enzymology* / Q000378:metabolism; D002855:Chromatography, Thin Layer; D003902:Detergents / Q000737:chemistry; D004970:Estrone / Q000378:metabolism; D005656:Fungal Proteins / Q000302:isolation & purification* / Q000378:metabolism; D008565:Membrane Proteins / Q000302:isolation & purification* / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D000438:Alcohols; D001643:Bridged Bicyclo Compounds; D003902:Detergents; D005656:Fungal Proteins; D008565:Membrane Proteins; C487951:bicyclo(2.2.2)octane-2,6-dione; D004970:Estrone; D000429:Alcohol Oxidoreductases; D009247:NADH, NADPH Oxidoreductases