A novel direct homogeneous assay for ATP citrate lyase |
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Authors: | Zhengping Ma Ching-Hsuen Chu and Dong Cheng |
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Institution: | Department of Metabolic Research, Research and Development, Bristol-Myers Squibb Company, Princeton, NJ 08543-5400 |
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Abstract: | ATP citrate lyase (ACL) is a cytosolic enzyme that catalyzes the synthesis of acetyl-CoA and oxaloacetate using citrate, CoA, and ATP as substrates and Mg2+ as a necessary cofactor. The ACL-dependent synthesis of acetyl-CoA is thought to be an essential step for the de novo synthesis of fatty acids and cholesterol. For this reason, inhibition of ACL has been pursued as a strategy to treat dyslipidemia and obesity. Traditionally, ACL enzyme activity is measured indirectly by coupling to enzymes such as malate dehydrogenase or chloramphenicol acetyl transferase. In this report, however, we describe a novel procedure to directly measure ACL enzyme activity. We first identified a convenient method to specifically detect 14C]acetyl-CoA without detecting 14C]citrate by MicroScint-O. Using this detection system, we devised a simple, direct, and homogeneous ACL assay in 384-well plate format that is suitable for high-throughput screening. The current assay consists of 1) incubation of ACL enzyme with 14C]citrate and other substrates/cofactors CoA, ATP, and Mg2+, 2) EDTA quench, 3) addition of MicroScint-O, the agent that specifically detects product 14C]acetyl-CoA, and 4) detection of signal by TopCount. This unique ACL assay may provide more efficient identification of new ACL inhibitors and allow detailed mechanistic characterization of ACL/inhibitor interactions. |
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Keywords: | fatty acid acetyl-CoA obesity dyslipidemia |
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