This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'The conversion of a fatty acid to an active fatty acid is catalysed by which of the following enzymes? \nSelect and explain. \nA. Acyl-CoA  synthetase, B. Enoyl CoA hydratase, C. Thiolase, D. Acyl CoA dehydrogenase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Fatty acids must first be converted to an active intermediate before they can be catabolized. This is the only step in\xa0the complete degradation of a fatty acid that requires energy from\xa0 ATP.\xa0 In\xa0 the\xa0 presence\xa0 of\xa0 ATP\xa0and\xa0coenzyme\xa0A,\xa0the enzyme\xa0acyl-CoA\xa0synthetase\xa0(thiokinase)\xa0catalyzes\xa0the conversion of a fatty acid (or FFA) to an “active fatty acid”\xa0or\xa0 acyl-CoA,\xa0using\xa0one\xa0high-energy\xa0phosphate\xa0and\xa0forming AMP and PPi . The PPi is hydrolyzed by inorganic pyrophosphatase with the loss of a further high-energy phosphate, ensuring that the overall reaction goes to completion.\xa0Acyl-CoA\xa0 synthetases\xa0 are\xa0 found\xa0 in\xa0 the\xa0 endoplasmic reticulum, peroxisomes, and inside and on the outer membrane of mitochondria.\nHARPERS ILLUSTRATED BIOCHEMISTRY30th ed page no. 224', 'role': 'assistant'}]