Miyabe Y, Amano T, Deyashiki Y, Hara A, Tsukada F
Gifu Pharmaceutical University, Japan.
Biol Pharm Bull. 1995 Jan;18(1):9-12. doi: 10.1248/bpb.18.9.
We have investigated the steady-state kinetics for a cytosolic 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase isozyme of human liver and its inhibition by several bile acids and anti-inflammatory drugs such as indomethacin, flufemanic acid and naproxen. Initial velocity and product inhibition studies performed in the NADP(+)-linked (S)-1-indanol oxidation at pH 7.4 were consistent with a sequential ordered mechanism in which NADP+ binds first and leaves last. The bile acids and drugs, competitive inhibitors with respect to the alcohol substrate, exhibited uncompetitive inhibition with respect to the coenzyme, with Ki values less than 1 microM, whereas indomethacin exhibited noncompetitive inhibition (Ki < 24 microM). The kinetics of the inhibition by a mixture of the two inhibitors suggests that bile acids and drugs, except indomethacin, bind to overlapping sites at the active center of the enzyme-coenzyme binary complex.
我们研究了人肝脏胞质3α-羟基类固醇/二氢二醇脱氢酶同工酶的稳态动力学，以及几种胆汁酸和消炎药物（如吲哚美辛、氟灭酸和萘普生）对其的抑制作用。在pH 7.4条件下，对与NADP(+)偶联的(S)-1-茚醇氧化反应进行的初速度和产物抑制研究，与一个有序序列机制相符，其中NADP+首先结合且最后离开。胆汁酸和药物作为醇底物的竞争性抑制剂，对辅酶表现出非竞争性抑制，其Ki值小于1 microM，而吲哚美辛表现出非竞争性抑制（Ki < 24 microM）。两种抑制剂混合物的抑制动力学表明，除吲哚美辛外，胆汁酸和药物在酶 - 辅酶二元复合物的活性中心结合于重叠位点。
