Paul H S, Adibi S A
J Biol Chem. 1982 May 10;257(9):4875-81.
The activity of branched-chain alpha-keto acid (BCKA) dehydrogenase was increased after preincubation of liver and muscle mitochondria of control rats. Preincubation depleted mitochondrial ATP. Addition of ATP prevented the activation of BCKA dehydrogenase as well as reversed the activity of a fully activated enzyme to normal. Inhibition of phosphatase blocked the activation of BCKA dehydrogenase. There was a small or no increase in BCKA dehydrogenase activity when mitochondria from tissues of fasted, diabetic, and clofibrate-treated rats were preincubated. In fasted and diabetic rats, ATP was either less effective or failed to reverse the increased dehydrogenase activity in preincubated mitochondria. The concentration of ATP in liver and muscle mitochondria of diabetic rats was approximately one-half that of the control rats. We conclude that (a) in the fed state approximately 30-40% of BCKA dehydrogenase exists in the active form. The enzyme can be fully activated by preincubation of mitochondria which causes the depletion of ATP. Phosphatase is necessary for this activation. (b) In fasted, diabetic, and clofibrate-treated rats, approximately 70-100% of the enzyme exists in the active form which may be related to the mitochondrial depletion of ATP in vivo, and (c) while ATP can reverse the activation in control rats, it fails to do so in diabetic rats suggesting that other metabolic alterations may be involved in the regulation of BCKA dehydrogenase in diabetes.
对照大鼠的肝脏和肌肉线粒体预孵育后，支链α-酮酸（BCKA）脱氢酶的活性增加。预孵育耗尽了线粒体ATP。添加ATP可阻止BCKA脱氢酶的激活，并使完全激活的酶的活性恢复正常。磷酸酶的抑制阻断了BCKA脱氢酶的激活。禁食、糖尿病和氯贝丁酯处理的大鼠组织线粒体预孵育时，BCKA脱氢酶活性仅有少量增加或无增加。在禁食和糖尿病大鼠中，ATP要么效果较差，要么无法逆转预孵育线粒体中脱氢酶活性的增加。糖尿病大鼠肝脏和肌肉线粒体中的ATP浓度约为对照大鼠的一半。我们得出结论：（a）在进食状态下，约30 - 40%的BCKA脱氢酶以活性形式存在。通过使线粒体预孵育导致ATP耗尽可使该酶完全激活。磷酸酶是这种激活所必需的。（b）在禁食、糖尿病和氯贝丁酯处理的大鼠中，约70 - 100%的酶以活性形式存在，这可能与体内线粒体ATP的耗尽有关，并且（c）虽然ATP可逆转对照大鼠中的激活，但在糖尿病大鼠中则不能，这表明糖尿病中BCKA脱氢酶的调节可能涉及其他代谢改变。
