Reijnierse G L, Veldstra H, Van der Ber C J
Biochem J. 1975 Dec;152(3):477-84. doi: 10.1042/bj1520477.
Acetyl-CoA synthase (EC 6.2.1.1), Propionyl-CoA synthase (EC 6.2.1.-) and butyryl-CoA synthase (EC 6.2.1.2) were measured in subcellular fractions prepared by primary and density-gradient fractionation from adult rat brain by a method resulting in recoveries close to 100%. Most of the activity of the three enzymes was recovered in the crude mitochondrial fraction. On subfractionation of this crude mitochondrial fraction with continuous sucrose density gradients, most of the activity of the three enzymes was found at a higher density than NAD+-isocitrate dehydrogenase and at about the same density as glutamate dehydrogenase, confirming earlier reported data for acetyl-CoA synthase. The finding that propionyl-CoA synthase and butyryl-CoA synthase had about the same distribution in the gradients as acetyl-CoA synthase adds support to the hypothesis that mitochondria involved in the metabolism of these short-chain fatty acids (all three of which have been shown to result in a rapid and high labelling of glutamine in vivo) form a distinct subpopulation of the total mitochondrial population. The three synthase activities were found to differ from each other in their rate of change and their subcellular localization during rat brain development. This, in combination with the observation that in gradients of adult brain preparations the three activities did not completely overlap, suggests that the three synthase activities are not present in the same proportion to each other in the same subpopulation (s) of mitochondria in the brain.
采用回收率接近100%的方法，对成年大鼠脑经初次分级和密度梯度分级制备的亚细胞组分中的乙酰辅酶A合酶（EC 6.2.1.1）、丙酰辅酶A合酶（EC 6.2.1.-）和丁酰辅酶A合酶（EC 6.2.1.2）进行了测定。这三种酶的大部分活性在粗线粒体组分中被回收。用连续蔗糖密度梯度对该粗线粒体组分进行再分级时，发现这三种酶的大部分活性位于比NAD⁺-异柠檬酸脱氢酶更高的密度处，且与谷氨酸脱氢酶的密度大致相同，这证实了先前关于乙酰辅酶A合酶的报道数据。丙酰辅酶A合酶和丁酰辅酶A合酶在梯度中的分布与乙酰辅酶A合酶大致相同，这一发现支持了以下假说：参与这些短链脂肪酸代谢的线粒体（所有这三种短链脂肪酸在体内均已被证明会导致谷氨酰胺迅速且高度标记）构成了整个线粒体群体中的一个独特亚群。研究发现，在大鼠脑发育过程中，这三种合酶活性在变化速率和亚细胞定位方面彼此不同。这一点，再加上在成年脑制备物的梯度中观察到这三种活性并未完全重叠，表明在脑中同一亚群的线粒体中，这三种合酶活性在彼此之间的比例并不相同。
