Monovalent cations and inorganic phosphate alter branched-chain alpha-ketoacid dehydrogenase-kinase activity and inhibitor sensitivity.
Monovalent cations and inorganic phosphate alter branched-chain alpha-ketoacid dehydrogenase-kinase activity and inhibitor sensitivity.
复制标题
单价阳离子和无机磷酸盐改变支链 α-酮酸脱氢酶激酶活性和抑制剂敏感性。
DOI：
10.1016/0003-9861(88)90252-4
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发表时间：
1988
影响因子：
3.9
通讯作者：
Harris,RA
中科院分区：
文献类型：
--
作者：
Shimomura,Y;Kuntz,MJ;Suzuki,M;Ozawa,T;Harris,RA
钾离子保护支链α-酮酸脱氢酶复合体免受热变性和蛋白酶消化的失活。铷是有效的，但钠和锂没有，这表明阳离子的离子大小对酶的稳定很重要。焦磷酸硫胺素络合物的稳定性研究[d]， D. J, lemon， S. K, and Elsas， S. J. (1980)Arch。物化学。生物物理学[j] . 2002,23 - 28]依赖于钾离子的存在。分解组分的研究表明，该复合物的硫胺素焦磷酸依赖酶，即2-氧异戊酸脱氢酶（脂酰胺）（EC 1.2.4.4）是钾离子稳定的组分。支链α-酮酸脱氢酶激酶活性测定方法表明，支链α-酮酸脱氢酶复合物失活在钾离子浓度为100 mm时达到最大。铷离子也能刺激激酶活性，而锂离子和钠离子则不能。所有测试的盐都增加了磷酸化失活的效率，即降低了导致复合物失活所需的酶磷酸化程度。α-氯异己酸酯作为支链α-酮酸脱氢酶激酶抑制剂的有效性和疗效在单价阳离子的存在下增强，在无机磷酸盐的存在下进一步增强。这些发现表明，单价阳离子和阴离子，特别是钾和磷酸盐，会引起脱氢酶激酶复合物的结构变化，从而改变其对磷酸化的敏感性和对激酶抑制剂的反应性。
Potassium ion protects the branched-chain α-ketoacid dehydrogenase complex against inactivation by thermal denaturation and protease digestion. Rubidium was effective but sodium and lithium were not, suggesting that the ionic size of the cation is important for stabilization of the enzyme. Thiamine pyrophosphate stabilization of the complex [Danner, D. J., Lemmon, S. K., and Elsas, S. J. (1980)Arch. Biochem. Biophys.202, 23–28] was found dependent on the presence of potassium ion. Studies with resolved components indicate that the thiamine pyrophosphate-dependent enzyme of the complex, i.e., the 2-oxoisovalerate dehydrogenase (lipoamide) (EC 1.2.4.4), is the component stabilized by potassium ion. Branched-chain α-ketoacid dehydrogenase-kinase activity measured by inactivation of the branched-chain α-ketoacid dehydrogenase complex was maximized at a potassium ion concentration of 100 mm. Stimulation of kinase activity was also found with rubidium ion but not with lithium and sodium ions. All salts tested increased the efficiency of inactivation by phosphorylation, i.e., decreased the degree of enzyme phosphorylation required to cause inactivation of the complex. The effectiveness and efficacy of α-chloroisocaproate as an inhibitor of branched-chain α-ketoacid dehydrogenase kinase were enhanced by the presence of monovalent cations, and further increased by inorganic phosphate. These findings suggest that monovalent cations and anions, particularly potassium and phosphate, cause structural changes in the dehydrogenase-kinase complex that alter its susceptibility to phosphorylation and responsiveness to kinase inhibitors.