title: Mycobacterium smegmatis fatty acid synthetase. A mechanism based on steady state rates and product distributions.
abstract: The initial steady state rate and product distribution of fatty acid synthesis catalyzed by Mycobacterium smegmatis fatty acid synthetase has been investigated as a function of various concentrations of acetyl-CoA, malonyl-CoA, mycobacterial polysaccharide, and bovine serum albumin. Polysaccharide has a large effect on both rate and chain length. The steady state rate stimulation by polysaccharide is not duplicated by other acyl-CoA-binding molecules such as bovine serum albumin. It is concluded that relief of product inhibition does not adequately explain the specific effects of the mycobacterial polysaccharide. A general mechanism is presented which accounts for variations in reaction rate and produce pattern over a wide range of experimental conditions. We propose that the diffusion of long chain acyl-CoA (C14 to C24) from the enzyme is the rate-limiting step in fatty acid synthesis catalyzed by the M. smegmatis synthetase. Polysaccharide facilitates this rate-limiting step by forming a ternary complex with enzyme-bound acyl-CoA causing rapid release of product.
mesh_terms: D000105:Acetyl Coenzyme A; D000217:Acyltransferases / Q000378:metabolism; D003065:Coenzyme A; D064429:Fatty Acid Synthases / Q000378:metabolism*; D007700:Kinetics; D008314:Malonates; D009161:Mycobacterium / Q000201:enzymology*; D011135:Polysaccharides, Bacterial / Q000502:physiology; D012710:Serum Albumin, Bovine; D013329:Structure-Activity Relationship
chemical_list: D008314:Malonates; D011135:Polysaccharides, Bacterial; D012710:Serum Albumin, Bovine; D000105:Acetyl Coenzyme A; D000217:Acyltransferases; D064429:Fatty Acid Synthases; D003065:Coenzyme A