Activity and intracellular distribution of enzymes of ketone-body metabolism in rat liver.
Activity and intracellular distribution of enzymes of ketone-body metabolism in rat liver.
复制标题
大鼠肝脏酮体代谢酶的活性和细胞内分布。
作者：
D. Williamson;M. Bates;H. Krebs
1.羟甲基戊二酰辅酶A合酶和裂解酶在大鼠肝脏中的活动被发现是2 - 15倍，比其他作者在类似条件下报道的。2.当体重的基础上表示，没有明显的差异被发现之间的活动羟甲基戊二酰辅酶A合酶在整个肝匀浆正常和饥饿大鼠。在四氧嘧啶糖尿病大鼠和高脂饮食大鼠的肝脏中，合成酶活性分别增加了70%和140%。3.羟甲基戊二酰辅酶A裂解酶活性没有显着增加饥饿或四氧嘧啶糖尿病，但增加了40%，发现在脂肪喂养的大鼠。4.这两种酶的活性的不到12%被发现在正常肝脏的细胞质部分。在四氧嘧啶糖尿病和饥饿的细胞质活动增加了一倍，喂养高脂肪饮食的增加，虽然显着，是不太明显。6.谷氨酸脱氢酶的细胞内分布表明，观察到的细胞质活性的变化不是由于从线粒体泄漏。7. 48小时后喂以正常或高脂肪饲料。24小时内造成饥饿。羟甲基戊二酰-CoA合酶的细胞质活性降低至低于在较长时间内喂食相应饮食的大鼠中发现的值。8.肝脏中的乙酰乙酰辅酶A脱酰酶活性约为羟甲基戊二酰辅酶A合酶活性的20%，主要位于细胞质中。饥饿或四氧嘧啶糖尿病没有改变乙酰乙酰辅酶A脱酰酶活性。9.它的结论是参与乙酰乙酸合成的酶的浓度的变化在调节酮体形成在饥饿和四氧嘧啶糖尿病中没有发挥重要作用。羟甲基戊二酰辅酶A合酶和裂解酶的细胞质活性的变化表明，乙酰乙酸合成可以发生在细胞质中。当脂肪生成被抑制时，这可能在处理细胞质中产生的多余乙酰辅酶A中起作用。
1. The activities of hydroxymethylglutaryl-CoA synthase and lyase in rat liver were found to be two- to 15-fold greater than those reported by other authors under similar conditions. 2. When expressed on the basis of body weight, no appreciable differences were found between the activities of hydroxymethylglutaryl-CoA synthase in whole homogenates of livers from normal and starved rats. The synthase activity increased by 70% and 140% in livers of alloxan-diabetic rats and rats fed on a high-fat diet respectively. 3. Hydroxymethylglutaryl-CoA lyase activity showed no significant increases in starvation or alloxan-diabetes, but a 40% increase was found in fat-fed rats. 4. Less than 12% of the activities of both enzymes were found in the cytoplasmic fraction of normal liver. The cytoplasmic activity doubled in alloxan-diabetes and starvation; on feeding with a high-fat diet the increase, though significant, was less marked. 6. The intracellular distribution of glutamate dehydrogenase indicated that the changes in the cytoplasmic activities observed were not due to leakage from the mitochondria. 7. Feeding with a normal or high-fat diet after 48hr. starvation caused within 24hr. a decrease in the cytoplasmic activity of hydroxymethylglutaryl-CoA synthase to values lower than those found in rats fed on a corresponding diet for a longer period of time. 8. Acetoacetyl-CoA deacylase activity in liver was about 20% of that of hydroxymethylglutaryl-CoA synthase and was primarily located in the cytoplasm. Starvation or alloxan-diabetes did not alter the acetoacetyl-CoA deacylase activity. 9. It is concluded that variations in the concentrations of enzymes involved in acetoacetate synthesis play no major role in the regulation of ketone-body formation in starvation and alloxan-diabetes. The changes in the cytoplasmic activities of hydroxymethylglutaryl-CoA synthase and lyase suggest that acetoacetate synthesis can occur in the cytoplasm. This may play a role in the disposal of surplus acetyl-CoA arising in the cytoplasm when lipogenesis is inhibited.