家兎水晶体Aldose Reductase IIの基質特異性と種々の化合物による阻害

抄録

The properties of two enzymes, aldose reductase IIa and IIb, with DL-glyceraldehyde reductase activity in rabbit lens were investigated, and compared with those of aldose reductase I's from rabbit lens described in the previous paper. Both aldose reductases IIa and IIb showed similar substrate specificity, and were capable of reducing various aldoses and aldehydes. These enzymes used nicotinamide adenine dinucleotide phosphate (NADPH) as coenzyme specifically. Aldose reductase II's and aldose reductase I's acted on common substrates, but the K_m values for substrates of aldose reductase II's were higher than those of aldose reductase I's. NADP⁺ and adenosine 2', 5'-diphosphate (2', 5'-ADP) were strong competitive inhibitors of aldose reductase II's with respect to the coenzyme. The K_i values for NADP⁺ and 2', 5'-ADP of aldose reductase II's were about 60μM and 7μM, respectively, and these values were smaller than those of aldose reductase I's. Aldose reductase II's were inhibited strongly by aldose reductase inhibitors such as quercitrin, quercetin and 3, 3-tetramethyleneglutaric acid, but the susceptibility of aldose reductase II's against these inhibitors was lower than that of aldose reductase I's.