Strukova S M, Semenova O A, Kireeva E G
Biokhimiia. 1980 Apr;45(4):738-46.
Indole was shown to stimulate TAME hydrolysis by alpha-thrombin with KA=7,7 mM, alpha=0,55, beta=1,5 and that by beta/gamma-thrombin with KA=9,5 mM, alpha=0,47 and beta=2,08. Indole promotes both the formation and transformation of the enzyme-substrate complex. No effect of substrate activation was observed in the presence of indole, which suggests the identity of the binding sites of indole and the added TAME molecule. Heparin was shown to form an equimolar stoicheometric complex with both alpha- and beta/gamma-thrombin, which results in 40% inhibition of the TAME-esterase, clotting and prothrombinolytic activities of alpha-thrombin and 25% and 40% inhibition of the TAME-esterase and prothrombinolytic activity of beta/gamma-thrombin, respectively. The fact that alpha- and beta/gamma-thrombin partially retain their catalytic properties even at a 5-fold molar excess of the inhibitor indicates that heparin binds to the thrombin molecule at a site other than the active center. Heparin does not prevent the effect of substrate activation at high TAME concentrations. This finding suggests that the localization of binding sites of heparin and the added TAME molecule (and, therefore, indole) in the thrombin molecule is different.
吲哚可刺激α-凝血酶水解TAME，其解离常数KA = 7.7 mM，α = 0.55，β = 1.5；也可刺激β/γ-凝血酶水解TAME，其解离常数KA = 9.5 mM，α = 0.47，β = 2.08。吲哚可促进酶 - 底物复合物的形成与转化。在吲哚存在的情况下未观察到底物激活效应，这表明吲哚与添加的TAME分子的结合位点相同。肝素与α-凝血酶和β/γ-凝血酶均形成等摩尔化学计量复合物，这导致α-凝血酶的TAME酯酶活性、凝血活性和凝血酶原激活活性分别受到40%的抑制，β/γ-凝血酶的TAME酯酶活性和凝血酶原激活活性分别受到25%和40%的抑制。即使抑制剂的摩尔过量为5倍，α-凝血酶和β/γ-凝血酶仍部分保留其催化特性，这一事实表明肝素在凝血酶分子上的结合位点并非活性中心。在高TAME浓度下，肝素并不阻止底物激活效应。这一发现表明肝素与添加的TAME分子（因此还有吲哚）在凝血酶分子中的结合位点定位不同。
