Deana R, Rigoni F, Deana A D, Galzigna L
Biochim Biophys Acta. 1981 Nov 13;662(1):119-24. doi: 10.1016/0005-2744(81)90231-x.
The presence and the localization of the enzyme catalyzing the transfer of a coenzyme A molecule from succinyl-CoA to 3-hydroxy-3-methylglutarate has been established in rat liver mitochondria. The enzyme was found mainly in the mitochondrial matrix but some activity was also found in the inner membrane fraction. The enzyme has been purified about 100-fold from sonically-disrupted mitochondria by high-speed centrifugation, DEAE-cellulose chromatography, (NH4)2SO4 precipitation and Sephadex G-100 filtration. The enzymatic activity was recovered in the final step as a single peak. The coenzyme A transferase appears to have a molecular weight of 42 000, the highest activity at pH 8.5 and an energy of activation of 13 kcal/mol. Mercaptoethanol increases the activity and improves its stability. The enzyme is different from the succinylCoA: 3-oxoacids coenzyme A transferase and is active also on malonylCoA. The apparent Km values obtained for succinylCoA, malnylCoA and 3-hydroxy-3-methylglutarate were 2.2 . 10(-4) M, 3.7 . 10(-4) M and 1.7 . 10(-3) M, respectively. Acetoacetate, which is the final product of the mitochondrial metabolism of hydroxy-methylglutarylCoA, showed an inhibitory effect on the enzyme activity with a Ki of 0.5 mM. The physiological role of the enzyme is discussed.
在大鼠肝脏线粒体中已确定了催化辅酶A分子从琥珀酰辅酶A转移至3-羟基-3-甲基戊二酸的酶的存在及其定位。该酶主要存在于线粒体基质中，但在内膜部分也发现了一些活性。通过高速离心、DEAE-纤维素色谱法、硫酸铵沉淀和葡聚糖凝胶G-100过滤，已从经超声破碎的线粒体中将该酶纯化了约100倍。酶活性在最后一步以单一峰的形式回收。辅酶A转移酶的分子量似乎为42000，在pH 8.5时活性最高，活化能为13千卡/摩尔。巯基乙醇可提高活性并改善其稳定性。该酶不同于琥珀酰辅酶A：3-氧代酸辅酶A转移酶，对丙二酰辅酶A也有活性。琥珀酰辅酶A、丙二酰辅酶A和3-羟基-3-甲基戊二酸的表观米氏常数分别为2.2×10⁻⁴ M、3.7×10⁻⁴ M和1.7×10⁻³ M。羟甲基戊二酰辅酶A线粒体代谢的终产物乙酰乙酸对酶活性有抑制作用，抑制常数为0.5 mM。文中讨论了该酶的生理作用。
