Retzios A D, Rosenfeld R, Schiffman S
Department of Medicine, School of Medicine, University of Southern California, Los Angeles.
J Lab Clin Med. 1988 Nov;112(5):560-6.
Kinetic constants (Km and kcat) of kallikrein and factor XIa for the chromogenic substrates H-D-L-prolyl-L-phenylanyl-L-arginine-p-nitroanilide (S-2302) and L-pyroglutamyl-L-propyl-L-arginine-p-nitroanilide (S-2366) were determined. The determined constants allow the use of S-2302 and S-2366 in an assay that leads to the joint estimation of factor XI and prekallikrein in activated plasma. The assay reports approximately 3.1 micrograms/ml factor XIa and 34.5 micrograms/ml kallikrein in kaolin-activated plasma (kaolin content 2 mg/ml). The dual-substrate amidolytic assay shows good correlation with the coagulant assay of both factors (0.92 with the prekallikrein assay and 0.98 with the factor XI assay). It is capable, through the joint estimation of factor XI and prekallikrein levels, of differentiating among plasma samples deficient in components of the contact phase of blood coagulation. Kinetic constants of factor beta-XIIa (factor XII fragment) for these substrates and for N-benzol-L-isoleusyl-L-glutamyl-glycyl-L-arginine-P-nitro ani lide (S-2222) were determined, and they allowed the assessment of the contribution of this factor to this assay and its estimation in the activated phase.
测定了激肽释放酶和因子XIa对生色底物H-D- L-脯氨酰-L-苯丙氨酰-L-精氨酸-对硝基苯胺（S-2302）和L-焦谷氨酰-L-丙基-L-精氨酸-对硝基苯胺（S-2366）的动力学常数（Km和kcat）。所测定的常数使得S-2302和S-2366可用于一项能对活化血浆中的因子XI和前激肽释放酶进行联合测定的分析方法。该分析方法报告高岭土活化血浆（高岭土含量2mg/ml）中因子XIa约为3.1μg/ml，激肽释放酶约为34.5μg/ml。双底物酰胺水解分析与这两种因子的凝血分析显示出良好的相关性（与前激肽释放酶分析的相关性为0.92，与因子XI分析的相关性为0.98）。通过联合测定因子XI和前激肽释放酶水平，它能够区分凝血接触相成分缺乏的血浆样本。还测定了因子β-XIIa（因子XII片段）对这些底物以及对N-苯甲酰-L-异亮氨酰-L-谷氨酰-甘氨酰-L-精氨酸-p-硝基苯胺（S-2222）的动力学常数，这些常数有助于评估该因子对该分析方法的贡献及其在活化阶段的测定。
