RÉSUMÉ
Treatment of Chinese hamster ovary (CHO) cells by the aldehyde containing calpain inhibitor I resulted in the induction of a 35-kDa protein that was partially sequenced and shown to be a member of the aldo-keto reductase superfamily (Inoue, S., Sharma, R. C., Schimke, R. T., and Simoni, R. D. (1993) J. Biol. Chem. 268, 5894-5898). Using rapid amplification of cDNA ends polymerase chain reaction, we have sequenced the cDNA for this protein (CHO reductase). This enzyme is a new member of the aldo-keto reductase superfamily and shows greatest amino acid sequence identity to mouse fibroblast growth factor-regulated protein and mouse vas deferens protein (92 and 80% sequence identity, respectively). The enzyme exhibits about 70% sequence identity with the aldose reductases (ALR2; EC 1.1.1.21) and about 47% with the aldehyde reductases (ALR1; EC 1.1.1.2). Northern analysis showed that it is induced in preference to either ALR1 or ALR2 and RNase protection assays showed gene expression in bladder, testis, jejunum, and ovary in descending order of expression. The cDNA for this inducible reductase was cloned into the pET16b vector and expressed in BL21(DE3) cells. Expressed CHO reductase showed kinetic properties distinct from either ALR1 or ALR2 including the ability to metabolize ketones. This protein joins a growing number of inducible aldo-keto reductases that may play a role in cellular regulation and protection.