Purification and properties of an NADPH-linked aldehyde reductase from rat kidney

Rat kidney was shown to contain two NADPH-linked aldehyde reductases (alcohol:NADP+) oxidoreductase, EC 1.1.1.2) with different substrate affinities. The high-Km aldehyde reductase, which was purified to apparent homogeneity, had a molecular weight of 32 000 as determined by Sephadex G-100 gel filtration, and of 37 000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The purified enzyme reduced various aliphatic aldehydes of different carbon-chain lengths besides many chemicals containing aldehyde groups. The Km values for n-hexadecanal and n-octadecanal were 8 microM and 4 microM, respectively. Bovine serum albumin (1.8 mM) stimulated the reduction of n-hexadecanal and n-octadecanal, and increased the Vmax values by about 15-fold without changing the Km values. The kidney enzyme was not distinguishable from the brain and liver high-Km aldehyde reductases in mobility on polyacrylamide gel electrophoresis, immunological properties, peptide maps or substrate specificity.