Mori M, Matsue H, Miura S, Tatibana M, Hashimoto T
Eur J Biochem. 1985 May 15;149(1):181-6. doi: 10.1111/j.1432-1033.1985.tb08909.x.
Rat liver 3-ketoacyl-CoA thiolase, a mitochondrial matrix enzyme which catalyzes a step of fatty acid beta-oxidation, was synthesized in a rabbit reticulocyte lysate cell-free system. The in vitro product was apparently the same in molecular size and charge as the subunit of the mature enzyme. The enzyme synthesized in vitro was transported into isolated rat liver mitochondria in an energy-dependent manner. In pulse experiments with isolated rat hepatocytes at 37 degrees C, the radioactivity of the newly synthesized enzyme in the cytosolic fraction remained essentially unchanged during 5-20 min of incubation, whereas that of the enzyme in the particulate fraction increased with time during the incubation. The pulse-labeled enzyme disappeared with an apparent half-life of less than 3 min from the cytosolic fraction, in pulse-chase experiments. Purified 3-ketoacyl-CoA thiolase inhibited the mitochondrial uptake and processing of the precursors of the other matrix enzymes, ornithine carbamoyltransferase, medium-chain acyl-CoA dehydrogenase and acetoacetyl-CoA thiolase. These results indicate that 3-ketoacyl-CoA thiolase has an internal signal which is recognized by the mitochondria and suggest that this enzyme and the three others are transported into the mitochondria by a common pathway.
大鼠肝脏3-酮酰基辅酶A硫解酶是一种催化脂肪酸β-氧化步骤的线粒体基质酶，它在兔网织红细胞裂解物无细胞系统中合成。体外产物在分子大小和电荷方面显然与成熟酶的亚基相同。体外合成的酶以能量依赖的方式转运到分离的大鼠肝脏线粒体中。在37℃对分离的大鼠肝细胞进行脉冲实验时，在孵育5 - 20分钟期间，胞质部分新合成酶的放射性基本保持不变，而颗粒部分酶的放射性在孵育期间随时间增加。在脉冲追踪实验中，脉冲标记的酶从胞质部分消失的表观半衰期小于3分钟。纯化的3-酮酰基辅酶A硫解酶抑制其他基质酶（鸟氨酸氨甲酰基转移酶、中链酰基辅酶A脱氢酶和乙酰乙酰辅酶A硫解酶）前体的线粒体摄取和加工。这些结果表明3-酮酰基辅酶A硫解酶具有一个被线粒体识别的内部信号，并提示该酶和其他三种酶通过共同途径转运到线粒体中。
