The dissociation of carbon monoxide from hemoglobin intermediate.
The dissociation of carbon monoxide from hemoglobin intermediate.
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一氧化碳从血红蛋白中间体中解离。
DOI：
10.1016/s0021-9258(18)61224-4
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
L. Rossi
中科院分区：
文献类型：
--
作者：
M. Samaja;E. Rovida;M. Niggeler;M. Perrella;L. Rossi
为了研究人类血红蛋白中的变构转换机制，我们研究了配体（CO）从几个中间连接状态的解离，通过停流动力学技术，利用微过氧化物酶竞争性结合CO。研究的血红蛋白物质包括Hb（CO）4、双配体对称物质（alpha beta-CO）2和（alpha-CO beta）2，以及双配体和单配体不对称物质（alpha-CO beta-CO）（alpha beta）、（alpha-CO beta）（alpha beta-CO）、（alpha beta-CO）（alpha beta-CO）（alpha beta）和（alpha-CO beta）（alpha beta）。它们是通过用连二亚硫酸盐快速还原相应的化合价中间体而获得的，这些中间体又通过色谱法或杂交法获得。中间体的性质和浓度在-25 ℃下通过等电聚焦测定。在不同的血红蛋白浓度（0.1、0.02和0.001 mM [血红素]）、pH值（6.0、7.0、8.0）、有和无肌醇六磷酸的条件下进行研究。结果表明：（a）血红蛋白浓度在0.1-0.02 mM范围内不显著影响动力学速率;（B）α链比β链更快地解离CO;（c）对称的双配体中间体显示出与配体解离的协同性，该协同性在肌醇六磷酸存在下消失;（d）单配体中间体比双配体中间体更快地解离CO;（e）不对称双配体中间体在功能上不同于对称物质。
To investigate the mechanism of allosteric switching in human hemoglobin, we have studied the dissociation of the ligand (CO) from several intermediate ligation states by a stopped-flow kinetic technique that utilizes competitive binding of CO by microperoxidase. The hemoglobin species investigated include Hb(CO)4, the diliganded symmetrical species (alpha beta-CO)2 and (alpha-CO beta)2, and the di- and monoliganded asymmetrical species (alpha-CO beta-CO)(alpha beta), (alpha-CO beta)(alpha beta-CO), (alpha beta-CO) (alpha beta), and (alpha-CO beta)(alpha beta). They were obtained by rapid reduction with dithionite of the corresponding valence intermediates that in turn were obtained by chromatography or by hybridization. The nature and concentration of the intermediates were determined by isoelectric focusing at −25 degrees C. The study was performed at varying hemoglobin concentrations (0.1, 0.02, and 0.001 mM [heme]), pH (6.0, 7.0, 8.0), with and without inositol hexaphosphate. The results indicate that: (a) hemoglobin concentration in the 0.1-0.02 mM range does not significantly affect the kinetic rates; (b) the alpha chains dissociate CO faster than the beta chains; (c) the symmetrical diliganded intermediates show cooperativity with respect to ligand dissociation that disappears in the presence of inositol hexaphosphate; (d) the monoliganded intermediates dissociate CO faster than the diliganded intermediates; (e) the asymmetrical diliganded intermediates are functionally different from the symmetrical species.