Identification of reduced nicotinamide adenine dinucleotide phosphate-dependent aldehyde reductase in a Rhodotorula strain.

Reduced nicotinamide adenine dinucleotide phosphate (NADPH)-aldehyde reductase was isolated in 24% yield and 66-fold purification from a dl-glyceraldehyde-grown Rhodotorula species. This enzyme was specific for NADPH, and d-, l-, or dl-glyceraldehyde were equally good substrates. Other substrates had activities as follows: methylglyoxal, 50%; fructose, 33%; d- and l-arabinose, 12%; d-xylose, 8%; d-glucose, 5%; d-erythrose and d-threose, 0 to 5%. The product from the reduction of dl-glyceraldehyde was glycerol, as shown by high voltage electrophoresis, paper chromatography, and direct enzymatic analysis. Kinetic studies gave K(m) values of 0.89 mm and 0.013 mm for dl-glyceraldehyde and NADPH, respectively. An optimal pH range of 6.3 to 6.7 was found for maximal activity. Reduction of NADP(+) by glycerol was not demonstrable. This Rhodotorula NADPH-aldehyde reductase activity was compared to similar enzymes from other sources.