Carbonyl Reductase Activity Exhibited by Pig Testicular 20.BETA.-Hydroxysteroid Dehydrogenase.
作者:Shizuo NAKAJIN、Fumihiro TAMURA、Noriko TAKASE、Satoshi TOYOSHIMA
DOI:10.1248/bpb.20.1215
日期:——
The carbonyl reductase activity exhibited by pig testicular 20β-hydroxysteroid dehydrogenase (20β-HSD) was examined using a recombinant enzyme. Kinetic parameters were obtained for 48 carbonyl group-containing substrates, including aromatic aldehydes, aromatic ketones, cycloketones, quinones, aliphatic aldehydes and aliphatic ketones. 20β-HSD showed a high affinity towards quinones, such as 9, 10-phenanthrenequinone, α-naphthoquinone and menadione (Km values of 4, 2 and 5 μM, respectively), and the substrate utilization efficiency (Vmax/Km) of the enzyme against these quinones was very high. Cyclohexanone and 2-methylcyclohexanone were also reduced with a high Vmax/Km value, but not cyclopentanone or 2-methylcyclopentanone. Various aromatic aldehydes and ketones including benzaldehyde- and acetophenone-derivatives were reduced by 20β-HSD. Especially, 4-nitrobenzaldehyde and 4-nitroacetophenone were reduced with high Vmax/Km values in related compounds. The enzyme also reduced the pyridine-derivatives, 2-, 3-, and 4-benzoylpyridine, with the Vmax/Km value for 2-benzoylpyridine being the highest. 20β-HSD reduced aliphatic aldehydes and aliphatic ketones, but was more effective on the former. The correlation between the structure of carbonyl compounds and their substrate Vmax/Km is discussed.
利用重组酶检测了猪睾丸20β-羟基类固醇脱氢酶(20β-HSD)表现出的羰基还原酶活性。获得了包括芳香醛、芳香酮、环酮、醌、脂肪醛和脂肪酮在内的48种含羰基基团底物的动力学参数。20β-HSD对醌类如9,10-菲醌、α-萘醌和维生素K3表现出高亲和性(Km值分别为4、2和5 μM),且该酶对这些醌的底物利用效率(Vmax/Km)非常高。环己酮和2-甲基环己酮也以高Vmax/Km值被还原,但环戊酮和2-甲基环戊酮未被还原。各种芳香醛和酮类包括苯甲醛和苯乙酮的衍生物均被20β-HSD还原。尤其是,4-硝基苯甲醛和4-硝基苯乙酮在相关化合物中以高Vmax/Km值被还原。该酶也还原吡啶衍生物,2-、3-和4-苯甲酰吡啶,其中2-苯甲酰吡啶的Vmax/Km值最高。20β-HSD还原脂肪醛和脂肪酮,但对前者的还原效率更高。讨论了羰基化合物的结构和其底物Vmax/Km之间的相关性。