title: A Novel Aldo-Keto Reductase, HdRed, from the Pacific Abalone Haliotis discus hannai, Which Reduces Alginate-derived 4-Deoxy-L-erythro-5-hexoseulose Uronic Acid to 2-Keto-3-deoxy-D-gluconate.
abstract: Abalone feeds on brown seaweeds and digests seaweeds' alginate with alginate lyases (EC 4.2.2.3). However, it has been unclear whether the end product of alginate lyases (i.e. unsaturated monouronate-derived 4-deoxy-L-erythro-5-hexoseulose uronic acid (DEH)) is assimilated by abalone itself, because DEH cannot be metabolized via the Embden-Meyerhof pathway of animals. Under these circumstances, we recently noticed the occurrence of an NADPH-dependent reductase, which reduced DEH to 2-keto-3-deoxy-D-gluconate, in hepatopancreas extract of the pacific abalone Haliotis discus hannai. In the present study, we characterized this enzyme to some extent. The DEH reductase, named HdRed in the present study, could be purified from the acetone-dried powder of hepatopancreas by ammonium sulfate fractionation followed by conventional column chromatographies. HdRed showed a single band of ∼ 40 kDa on SDS-PAGE and reduced DEH to 2-keto-3-deoxy-D-gluconate with an optimal temperature and pH at around 50 °C and 7.0, respectively. HdRed exhibited no appreciable activity toward 28 authentic compounds, including aldehyde, aldose, ketose, α-keto-acid, uronic acid, deoxy sugar, sugar alcohol, carboxylic acid, ketone, and ester. The amino acid sequence of 371 residues of HdRed deduced from the cDNA showed 18-60% identities to those of aldo-keto reductase (AKR) superfamily enzymes, such as human aldose reductase, halophilic bacterium reductase, and sea hare norsolorinic acid (a polyketide derivative) reductase-like protein. Catalytic residues and cofactor binding residues known in AKR superfamily enzymes were fairly well conserved in HdRed. Phylogenetic analysis for HdRed and AKR superfamily enzymes indicated that HdRed is an AKR belonging to a novel family.
authors.affiliation: From the Laboratory of Marine Biotechnology and Microbiology, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Mochizuki
authors.affiliation: From the Laboratory of Marine Biotechnology and Microbiology, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Nishiyama
authors.affiliation: From the Laboratory of Marine Biotechnology and Microbiology, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Inoue
authors.affiliation: From the Laboratory of Marine Biotechnology and Microbiology, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan ojima@fish.hokudai.ac.jp.
authors.forename: Takao
authors.initials: T
authors.lastname: Ojima
mesh_terms: D000449:Aldehyde Reductase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000074408:Aldo-Keto Reductases; D000464:Alginates / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D049851:Gastropoda / Q000201:enzymology* / Q000235:genetics; D005942:Gluconates / Q000737:chemistry* / Q000378:metabolism; D020723:Glucuronic Acid / Q000737:chemistry / Q000378:metabolism; D043143:Hepatopancreas / Q000201:enzymology*; D006603:Hexuronic Acids / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D010084:Oxidation-Reduction; D017386:Sequence Homology, Amino Acid
chemical_list: D000464:Alginates; D005942:Gluconates; D006603:Hexuronic Acids; C081217:2-keto-3-deoxy-6-phosphogluconate; D020723:Glucuronic Acid; D000074408:Aldo-Keto Reductases; D000449:Aldehyde Reductase
keywords: DEH reductase; abalone; aldo-keto reductase; alginate; alginate lyase; alginate metabolism; enzyme; invertebrate; metabolism; polysaccharide