Molecular characterization of mammalian dicarbonyl/L-xylulose reductase and its localization in kidney.
In this report, we first cloned a cDNA for a protein that is highly expressed in mouse kidney and then isolated its counterparts in human, rat hamster, and guinea pig by polymerase chain reaction-based cloning. The cDNAs of the five species encoded polypeptides of 244 amino acids, which shared more than 85% identity with each other and showed high identity with a human sperm 34-kDa protein, P34H, as well as a murine lung-specific carbonyl reductase of the short-chain dehydrogenase/reductase superfamily. In particular, the human protein is identical to P34H, except for one amino acid substitution. The purified recombinant proteins of the five species were about 100-kDa homotetramers with NADPH-linked reductase activity for alpha-dicarbonyl compounds, catalyzed the oxidoreduction between xylitol and l-xylulose, and were inhibited competitively by n-butyric acid. Therefore, the proteins are designated as dicarbonyl/l-xylulose reductases (DCXRs). The substrate specificity and kinetic constants of DCXRs for dicarbonyl compounds and sugars are similar to those of mammalian diacetyl reductase and l-xylulose reductase, respectively, and the identity of the DCXRs with these two enzymes was demonstrated by their co-purification from hamster and guinea pig livers and by protein sequencing of the hepatic enzymes. Both DCXR and its mRNA are highly expressed in kidney and liver of human and rodent tissues, and the protein was localized primarily to the inner membranes of the proximal renal tubules in murine kidneys. The results imply that P34H and diacetyl reductase (EC ) are identical to l-xylulose reductase (EC ), which is involved in the uronate cycle of glucose metabolism, and the unique localization of the enzyme in kidney suggests that it has a role other than in general carbohydrate metabolism.
Nakagawa
Junichi
J
Medicinal Research Laboratories, Taisho Pharmaceutical Co., Ltd., 1-403 Yoshino-cho, Saitama-shi, Saitama 330-8530, Japan. junichi.nakagawa@po.rd.taisho.co.jp
Ishikura
Syuhei
S
Asami
Jun
J
Isaji
Tomoya
T
Usami
Noriyuki
N
Hara
Akira
A
Sakurai
Takanobu
T
Tsuritani
Katsuki
K
Oda
Koji
K
Takahashi
Masayoshi
M
Yoshimoto
Makoto
M
Otsuka
Noboru
N
Kitamura
Kunihiro
K
D000094:Acetoin Dehydrogenase / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D003001:Cloning, Molecular; D006224:Cricetinae; D004591:Electrophoresis, Polyacrylamide Gel; D006168:Guinea Pigs; D006801:Humans; D007668:Kidney / Q000201:enzymology*; D008969:Molecular Sequence Data; D051381:Rats; D016415:Sequence Alignment; D013401:Sugar Alcohol Dehydrogenases / Q000737:chemistry / Q000378:metabolism*
D000429:Alcohol Oxidoreductases; D013401:Sugar Alcohol Dehydrogenases; D000094:Acetoin Dehydrogenase; C023300:L-xylulose reductase