DMF竞争性抑制大豆脂氧酶好氧催化及其松弛底物抑制的综合作用

Effects of DMF on Competitive Inhibition of Lipoxygenase and Relaxation of Substrate Inhibition in Aerobic Catalysis of Lipoxygenase

在大豆脂氧酶催化亚油酸的氧化反应中加入溶剂二甲基甲酰胺DMF(lgP为-1.01)可将底物亚油酸浓度提升到232 mmol/L而不产生底物抑制作用,并使平衡产率从38.93%提高到66.09%.在有底物存在时,质量分数为5%的DMF基本不影响酶活;此时体系具有最大的Kss与Ki值,表明5%DMF对底物抑制作用的松弛效应最强,而对酶的抑制作用最小.

The substrate inhibition was observed in the hydroperoxidation of linoleic acid catalyzed by soybean lipoxygenase at substrate concentrations higher than 0. 075 mmol/L. Addition of DMF （ 1gP = 1. 01 ） could raise the substrate level to 232 mmol/L, and increase the hydroperoxide （HPOD） yield from 38.93% to 66. 09%. The results of lyophilization test show that DMF mixed with substrate didnt influence on the enzymatic activity evidently although DMF made the enzymatic activity declined obviously in the absence of substrate. For lipoxygenase DMF served as either an activator at lower level or an inhibitor at higher level, which was illustrated by the activation constant Ka, the inhibition constant Ki and the effect of DMF with substrate on enzymatic activity. The snhstrate inhibition constant Kss at higher DMF level increased by 1000-5600 folds, which implied that the interaction between relaxation of snhstrate inhibition and competitive inhibition of lipoxygenase resulted from DMF made the excess substrate inhibition greatly released. The maximum Kss and Ki obtained at 5% DMF means that the maximum relaxation of substrate inhibition and the minimum competitive inhibition to lipoxygenase appeared simultaneously.