Wang Yan-Lin, Guo Wen, Zang Yan, Yaney Gordon C, Vallega Gino, Getty-Kaushik Lisa, Pilch Paul, Kandror Konstantin, Corkey Barbara E
Department of Medicine, Obesity Research Center, Boston University School of Medicine, Boston, MA 02118, USA.
Obes Res. 2004 Nov;12(11):1781-8. doi: 10.1038/oby.2004.221.
Long-chain acyl coenzyme A synthetase (ACSL) converts free fatty acids (FFAs) into their metabolizable long-chain acyl coenzyme A (LC-CoA) derivatives that are essential for FFA conversion to CO(2), triglycerides, or complex lipids. ACSL-1 is highly expressed in adipose tissue with broad substrate specificity. We tested the hypothesis that ACSL localization, and resulting local generation of LC-CoA, regulates FFA partitioning.
These studies used cell fractionation of rat adipocytes to measure ACSL activity and mass and compared cells from young, mature, fed, fasted, and diabetic rats. Functional studies included measurement of FFA oxidation, complex lipid synthesis, and LC-CoA levels.
High ACSL specific activity was expressed in the mitochondria/nuclei (M/N), high-density microsomes (HDM), low-density microsomes (LDM), and plasma membrane (PM) fractions. We show here that, during fasting, total FFA oxidation increased, and, although total ACSL activity decreased, a greater percentage of activity (43 +/- 1.5%) was associated with the M/N fraction than in the fed state (23 +/- 0.3%). In the fed state, more ACSL activity (34 +/- 0.5%) was associated with the HDM than in the fasted state (25 +/- 0.9%), concurrent with increased triglyceride formation from FFA. Insulin increased LC-CoA and ACSL activity associated with the PM. The changes in ACSL activity in response to insulin were associated with only minor changes in mass as determined by Western blotting.
It is hypothesized that ACSL plays an important role in targeting FFA to specific metabolic pathways or acylation sites in the cell, thus acting as an important control mechanism in fuel partitioning. Localization of ACSL at the PM may serve to decrease FFA efflux and trap FFA within the cell as LC-CoA.
长链脂酰辅酶A合成酶（ACSL）将游离脂肪酸（FFA）转化为可代谢的长链脂酰辅酶A（LC-CoA）衍生物，这些衍生物对于FFA转化为二氧化碳、甘油三酯或复合脂质至关重要。ACSL-1在脂肪组织中高度表达，具有广泛的底物特异性。我们检验了以下假设：ACSL的定位以及由此产生的LC-CoA的局部生成调节FFA的分配。
这些研究采用大鼠脂肪细胞的细胞分级分离法来测量ACSL活性和含量，并比较了来自年轻、成熟、喂食、禁食和糖尿病大鼠的细胞。功能研究包括测量FFA氧化、复合脂质合成和LC-CoA水平。
高ACSL比活性在线粒体/细胞核（M/N）、高密度微粒体（HDM）、低密度微粒体（LDM）和质膜（PM）组分中表达。我们在此表明，在禁食期间，总FFA氧化增加，并且尽管总ACSL活性降低，但与M/N组分相关的活性百分比（43±1.5%）高于喂食状态（23±0.3%）。在喂食状态下，与HDM相关联的ACSL活性（34±0.5%）高于禁食状态（25±0.9%），同时FFA生成甘油三酯增加。胰岛素增加了与PM相关的LC-CoA和ACSL活性。通过蛋白质印迹法测定，ACSL活性对胰岛素的反应变化仅伴随着含量的微小变化。
据推测，ACSL在将FFA靶向细胞内特定代谢途径或酰化位点方面起重要作用，因此在燃料分配中作为一种重要的控制机制。ACSL在PM处的定位可能有助于减少FFA流出并将FFA作为LC-CoA捕获在细胞内。
