Antonini G, Bellelli A, Brunori M, Falcioni G
Department of Biochemical Sciences, University of Rome 'La Sapienza', Italy.
Biochem J. 1996 Mar 1;314 ( Pt 2)(Pt 2):533-40. doi: 10.1042/bj3140533.
The cyanide ion is a ligand of ferrous as well as ferric haemoproteins and this study presents a kinetic characterization of the dissociation of its complexes with the two main haemoglobin components from trout blood. Both these haemoglobins bind oxygen co-operatively at neutral or alkaline pH values but one of them is insensitive to pH and allosteric effectors (haemoglobin I, HbI) while the other (haemoglobin IV, HbIV) is strongly sensitive and shows the so-called Root effect (i.e. the incomplete oxygen saturation in air-equilibrated solutions at pH values of < 6.5). Comparison of the kinetics of dissociation of cyanide from ferrous forms of HbI and HbIV reveals that: (i) cyanide dissociates in both cases by a complex reaction, and, at least in the case of HbIV, this may be attributed to functional differences between the alpha and beta subunits; (ii) the reaction is only scarcely co-operative in HbI and not at all so in HbIV; and (iii) the Bohr and Root effects are not manifested in this reaction. The functional heterogeneity of ferrous alpha and beta chains of trout HbI has not been observed for any other ligand; moreover, the observation that co-operativity for cyanide dissociation is expressed by human haemoglobin but not by trout HbIV is surprising.
氰离子是亚铁血红蛋白和高铁血红蛋白的配体，本研究对其与鳟鱼血液中两种主要血红蛋白成分形成的复合物的解离进行了动力学表征。这两种血红蛋白在中性或碱性pH值下都能协同结合氧气，但其中一种对pH值和变构效应剂不敏感（血红蛋白I，HbI），而另一种（血红蛋白IV，HbIV）则非常敏感，并表现出所谓的鲁特效应（即在pH值<6.5的空气平衡溶液中氧饱和度不完全）。对HbI和HbIV亚铁形式的氰化物解离动力学进行比较后发现：（i）在两种情况下，氰化物都是通过复杂反应解离的，至少在HbIV的情况下，这可能归因于α亚基和β亚基之间的功能差异；（ii）该反应在HbI中仅有微弱的协同性，在HbIV中则完全没有；（iii）该反应未表现出玻尔效应和鲁特效应。对于任何其他配体，均未观察到鳟鱼HbI亚铁α链和β链的功能异质性；此外，人血红蛋白表现出氰化物解离的协同性，而鳟鱼HbIV却没有，这一观察结果令人惊讶。
