title: Purification and some properties of a medium-chain acyl-thioester hydrolase from lactating-rabbit mammary gland which terminates chain elongation in fatty acid synthesis.
abstract: 1. An acyl-thioester hydrolase was isolated from the cytosol of lactating-rabbit mammary gland. The purified enzyme terminates fatty acid synthesis at medium-chain (C8:0-C12:0) acids when it is incubated with fatty acid synthetase and rate-limiting concentrations of malonyl-CoA. These acids are characteristic products of the lactating gland. 2. The mol.wt. of the enzyme is 29000+/-500 (mean+/-S.D. of three independent preparations), as estimated by polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. 3. The enzyme also hydrolyses acyl-CoA esters of chain lengths C10:0-C16:0 when these are used as model substrates. The greatest activity was towards dodecanoyl-CoA, and the three preparations had specific activities of 305, 1130 and 2010 nmol of dodecanoyl-CoA hydrolysed/min per mg of protein when 56muM substrate was used. 4. The way in which this enzyme controls the synthesis of medium-chain fatty acids by fatty acid synthetase is briefly discussed.
mesh_terms: D000418:Albumins / Q000494:pharmacology; D000818:Animals; D003065:Coenzyme A / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis*; D005260:Female; D006867:Hydrolases / Q000378:metabolism; D007774:Lactation; D008321:Mammary Glands, Animal / Q000201:enzymology*; D008970:Molecular Weight; D011247:Pregnancy; D011817:Rabbits; D013869:Thiolester Hydrolases / Q000302:isolation & purification*
chemical_list: D000418:Albumins; D005227:Fatty Acids; D006867:Hydrolases; D013869:Thiolester Hydrolases; D003065:Coenzyme A