Agius L, Wright P D, Alberti K G
Clin Sci (Lond). 1987 Jul;73(1):3-10. doi: 10.1042/cs0730003.
The activities of carnitine acyltransferases and acyl-CoA hydrolases were determined in human and rat liver to establish the validity of extrapolating from studies on rats to human metabolism. In human liver, carnitine acetyltransferase activity was 10-14 times higher and carnitine octanoyltransferase 1.7-2.4 times higher than in rat liver, while carnitine palmitoyltransferase activity was similar in human and rat. Acetyl-CoA hydrolase and octanoyl-CoA hydrolase activities were lower in human (42-57%) than in rat liver, but palmitoyl-CoA hydrolase activity was similar in both species. The activity of citrate synthase was lower (44%) in human than in rat liver. The low citrate synthase activity and the high carnitine acetyltransferase in human liver suggest that in man acetylcarnitine might be more important as a vehicle for export of acetyl units from mitochondria than citrate. The high activity of carnitine acetyltransferase in human liver is consistent with the observation that acetylcarnitine is the predominant acylcarnitine excreted in diabetic ketosis in man. It is concluded that the rat may not be a valid model for carnitine metabolism in man, and that in human liver carnitine may have an important role in transfer of acetyl groups out of mitochondria and possibly also to extra-hepatic tissues.
测定了人和大鼠肝脏中肉碱酰基转移酶和酰基辅酶A水解酶的活性，以确定从大鼠研究推断人类代谢的有效性。在人肝脏中，肉碱乙酰转移酶活性比大鼠肝脏高10 - 14倍，肉碱辛酰转移酶高1.7 - 2.4倍，而肉碱棕榈酰转移酶活性在人和大鼠中相似。乙酰辅酶A水解酶和辛酰辅酶A水解酶活性在人肝脏中比大鼠肝脏低（42 - 57%），但棕榈酰辅酶A水解酶活性在两个物种中相似。人肝脏中柠檬酸合酶的活性比大鼠肝脏低（44%）。人肝脏中柠檬酸合酶活性低和肉碱乙酰转移酶活性高表明，在人类中，乙酰肉碱作为线粒体中乙酰单位输出的载体可能比柠檬酸更重要。人肝脏中肉碱乙酰转移酶的高活性与人类糖尿病酮症中乙酰肉碱是主要排出的酰基肉碱这一观察结果一致。结论是，大鼠可能不是人类肉碱代谢的有效模型，并且在人肝脏中，肉碱可能在将乙酰基团从线粒体转运到肝外组织中发挥重要作用。
