中文摘要：

肠激酶（EK,EC 3.4.21.9）是一种在基因工程产品中广泛应用的工具酶.以小分子荧光物质Gly-Asp-Asp-Asp-Asp-Lys-β-萘胺为底物,采用荧光跟踪法研究了变性剂盐酸胍、硫脲、尿素对重组牛肠激酶（rEK）活力的影响及抑制动力学.结果表明：盐酸胍、硫脲、尿素均对该酶的活性有较强的抑制作用,它们对该酶的半抑制浓度（IC50）分别为0.025,0.080和0.750 mol/L.研究的3种变性剂对该酶的抑制均显示可逆抑制机理;抑制类型也均为竞争性类型,测定它们对酶的抑制常数KI分别为0.015,0.060和0.553 mol/L.

英文摘要：

Enterokinase（EK,EC 3.4.21.9）is an important enzyme widely used in gene engineering.In this study,the inhibitory effects of several denaturant guanidine hydrochloride,thiourea and urea on the activity of rEK for the hydrolysis of Gly-Asp-Asp-Asp-Asp-Lys-β-naphthylamide were investigated by the monitoring the change of fluorescence.The results indicated that guanidine hydrochloride,thiourea and urea had strong inhibitory effect on the activity of rEK,with the concentrations of 0.025,0.080 and 0.750 mol/L,respectively leading to 50% enzyme activity lost.Research showed that the mechanism of guanidine hydrochloride,thiourea and urea effecting on rEK activity were reversible,belonging to competetive type inhibitory.The inhibition constants of guanidine hydrochloride,thiourea and urea were respectively 0.015,0.060 and 0.553 mol/L.