腈水合酶转化反应的影响因子

EFFECTORS ON THE CONVERSION REACTION OF NITRILEHYDRATASE FROM CORYNEBACTERIUM SP.ZBB-21

棒状杆菌(Corynebacterium sp.)ZBB-21腈水合酶能高效地将丙烯腈转化为丙烯酰胺,其转化反应的最适pH为8.0,最适转化反应温度为25℃。反应体系中加入微量的K^+、Na^+、Mg^(2+)和Fe^(3+)对酶的转化反应有明显的促进作用。过量丙烯腈(浓度为0.3mol/L以上)对酶活性有抑制作用,转化产物丙烯酰胺及其结构类似物丙烯酸是腈水合酶的竞争性抑制剂,其抑制常数K_i分别为0.06mol/L和0.70mol/L,游离氰离子(CN^-)的存在严重抑制丙烯酰胺的形成(K_i=1.25×10^(-3)mol/L)。

The optimum reaction conditions of nitrile-hydratase from Corynebacterium sp. ZBB-21 and the effects of different compounds on the enzyme action have been studied.The optimum pH was 8.0 for the enzymatic reaction of acrylonitrile-acryiamide bioconversion. The optimum reaction temperature was 25℃ and the reaction time was 10min. Some metal ions such as K^+, Na^+, Mg^(2+) and Fe^(3+) in reaction system could activate the activity of nitrile-hydratase.An excess of acrylonitrile as a substrate was shown to inhibit the enzyme activity. This inhibition occurred only at relatively high concentration of substrate (0.30 mol/L or more).A bioconversion product of acrylonitrile (acrylamide) and its structure analogue (acrylic acid) were shown to inhibit the nitrile-hydratase activity competitively. Their K_(?) were 0.06 mol/L and 0.70 mol/L respectively. The cyanide strongly inhibited the formation of acrylamide (K_1=1.25×10^(-3) mol/L).