Shinoda M, Hara A, Nakayama T, Deyashiki Y, Yamaguchi S
Gihoku General Hospital, Gifu.
J Biochem. 1992 Dec;112(6):840-4. doi: 10.1093/oxfordjournals.jbchem.a123986.
Dimeric dihydrodiol dehydrogenases from pig liver, monkey kidney, and rabbit lens were inhibited more potently by 4-hydroxyphenylketones such as 4-hydroxybenzaldehyde, 4-hydroxyphenylglyoxal, and 4-hydroxyacetophenone than by isoascorbate and ascorbate, known inhibitors of the enzymes. No significant inhibition was observed with 2- or 3-hydroxyphenylketones, phenylketones with a functional group other than a hydroxy group at the 4-position, and 4-hydroxyphenyl derivatives without a carbonyl group. The steady-state kinetic analyses of the inhibition of the pig liver enzyme indicated that the 4-hydroxyphenylketones, similarly to ascorbate and its epimer, bound to an enzyme-NADP+ binary complex as competitive inhibitors with respect to dihydrodiol substrate. The inhibition by the 4-hydroxyphenylketones was uncompetitive with respect to isoascorbate, and the addition of one of the 4-hydroxyphenylketones or isoascorbate with NADP+ afforded a great protective effect against inactivation of the enzyme by diethylpyrocarbonate or by heat treatment, which indicates that 4-hydroxyphenylketones and isoascorbate bind at the same site in or near the active center of the enzyme. The structural comparison of 4-hydroxybenzaldehyde and ascorbate suggests that the hydroxy group at C-5, carbonyl group at C-1 and lactone ring of ascorbate are important for the binding to the enzyme.
来自猪肝、猴肾和兔晶状体的二聚体二氢二醇脱氢酶，相较于已知的该酶抑制剂异抗坏血酸盐和抗坏血酸盐，4-羟基苯酮如4-羟基苯甲醛、4-羟基苯乙二醛和4-羟基苯乙酮对其抑制作用更强。2-或3-羟基苯酮、在4-位具有除羟基以外官能团的苯酮以及没有羰基的4-羟基苯衍生物未观察到明显抑制作用。对猪肝酶抑制作用的稳态动力学分析表明，4-羟基苯酮与抗坏血酸盐及其差向异构体类似，作为二氢二醇底物的竞争性抑制剂与酶-NADP+二元复合物结合。4-羟基苯酮对异抗坏血酸盐而言是非竞争性抑制，并且添加4-羟基苯酮之一或异抗坏血酸盐与NADP+一起对酶因焦碳酸二乙酯或热处理导致的失活具有很大的保护作用，这表明4-羟基苯酮和异抗坏血酸盐在酶活性中心内或其附近的同一部位结合。4-羟基苯甲醛和抗坏血酸盐的结构比较表明，抗坏血酸盐C-5位的羟基、C-1位的羰基和内酯环对于与酶的结合很重要。
