目的  建立一种丝氨酸蛋白酶抑制剂活性测定方法。方法  采用温控紫外分光光度计同时测定2种丝氨酸蛋白酶抑制剂，重组Textilinin-1（recombinant Textilinin-1，Rtxln-1）与抑肽酶（aprotinin，AP）的抑制常数。优化活性测定方法的线性范围和孵育温度。应用此方法对Rtxln-1和AP进行活性测定，并对活性测定方法进行验证。结果  该方法的标准曲线拟合度决定系数≥0.98，测定Rtxln-1和AP的线性范围分别为10～50、0.056～0.560 nmol/L。Rtxln-1孵育温度为37 ℃，精密度的变异系数≤5%。结论  建立的丝氨酸蛋白酶抑制剂活性测定方法特异性高、拟合度优，对Rtxln-1活性测定的精密度好，可用于AP、Rtxln-1等胰蛋白酶抑制剂的生物学活性的测定，也可用于广泛的丝氨酸蛋白酶抑制剂的活性测定。

Objective  To establish a determination method for serine protease inhibitor activity. Methods  The inhibition constants of 2 serine protease inhibitors, recombinant Textilinin-1 (Rtxln-1) and aprotinin (AP), were determined at the same time using temperature-controlled ultraviolet spectrophotometer. The linear range and incubation temperature were optimized. The method was used to determine Rtxln-1 and AP activities, and was verified in Rtxln-1 activity determination. Result  The standard curves of both inhibitors had fitting coefficient of determination ≥0.98. The linear range was 10-50 nmol/L for Rtxln-1 and 0.056-0.560 nmol/L for AP. The optimal incubation temperature for Rtxlin-1 was 37 ℃, and coefficients of variation in all precision tests were ≤5%. Conclusion  The established method has high specificity, optimal curve fitting, good precision for Rtxln-1 activity determination. The method can be used for assessment of activity for trypsin inhibitors such as Rtxln-1 and AP, and for determination of general serine protease inhibitor activity.