Sallustio B C, Nunthasomboon S, Drogemuller C J, Knights K M
Department of Clinical Pharmacology, The Queen Elizabeth Hospital, Woodville, South Australia, 5011, Australia.
Toxicol Appl Pharmacol. 2000 Mar 1;163(2):176-82. doi: 10.1006/taap.1999.8868.
Endogenous fatty acyl-CoAs play an important role in the acylation of proteins. A number of xenobiotic carboxylic acids are able to mimic fatty acids, forming CoA conjugates and acting as substrates in pathways of lipid metabolism. In this study nafenopin, a substrate for human hepatic fatty acid-CoA ligases, was chosen as a model compound to study xenobiotic acylation of human liver proteins. (3)H-nafenopin (+/- unlabeled palmitate) or (14)C-palmitate (+/- unlabeled nafenopin) were incubated for up to 120 min at 37 degrees C with ATP, CoA, and homogenate protein (1 mg/ml) from four individual human livers. Nafenopin covalently bound to proteins was detectable in all human livers and increased with time. Nafenopin adduct formation was directly proportional to nafenopin-CoA formation (r = 0.985, p < 0.05). Attachment of nafenopin to proteins involved both thioester and amide linkages with 76 and 24% of adducts formed with proteins > 100 and 50-100 kDa, respectively. Protein acylation by palmitate was also demonstrated. Palmitate significantly inhibited nafenopin-CoA formation by 29% but had no effect on nafenopin-CoA-mediated protein acylation. In contrast, nafenopin significantly inhibited protein palmitoylation by palmitoyl-CoA. This is the first study to demonstrate a direct relationship between xenobiotic-CoA formation, acylation of human liver proteins, and inhibition of endogenous palmitoylation. The ability of xenobiotics to acylate tissue proteins may have important biological consequences including perturbation of endogenous regulation of protein localization and function.
内源性脂肪酰辅酶A在蛋白质酰化过程中发挥着重要作用。许多外源性羧酸能够模拟脂肪酸，形成辅酶A缀合物，并作为脂质代谢途径中的底物。在本研究中，选择作为人肝脂肪酸辅酶A连接酶底物的萘酚平作为模型化合物，以研究人肝蛋白质的外源性酰化作用。将（3）H-萘酚平（±未标记的棕榈酸酯）或（14）C-棕榈酸酯（±未标记的萘酚平）与ATP、辅酶A和来自四个人类肝脏个体的匀浆蛋白（1mg/ml）在37℃下孵育长达120分钟。在所有人的肝脏中均可检测到与蛋白质共价结合的萘酚平，且其含量随时间增加。萘酚平加合物的形成与萘酚平-辅酶A的形成直接成正比（r = 0.985，p < 0.05）。萘酚平与蛋白质的连接涉及硫酯键和酰胺键，分别有76%和24%的加合物与分子量大于100kDa和50 - 10 kDa的蛋白质形成。也证实了棕榈酸对蛋白质的酰化作用。棕榈酸显著抑制萘酚平-辅酶A的形成达29%，但对萘酚平-辅酶A介导的蛋白质酰化没有影响。相反，萘酚平显著抑制棕榈酰辅酶A对蛋白质的棕榈酰化作用。这是首次证明外源性辅酶A的形成、人肝蛋白质的酰化以及对内源性棕榈酰化的抑制之间存在直接关系的研究。外源性物质酰化组织蛋白质的能力可能具有重要的生物学后果，包括干扰蛋白质定位和功能的内源性调节。
