Elongation reactions, hydrocarbon biosynthesis

Vaz A. H., Blomquist G. J., Wakayama E. J. and Reitz R. C. (1987) Characterization of the fatty acyl elongation reactions involved in hydrocarbon biosynthesis in the housefly Musca domestica. Insect Biochem. 18, 177-184. 

Elongation Reactions Involved in Hydrocarbon Biosynthesis in Insects... 

To date, the elongation reactions involved in hydrocarbon biosynthesis have only been examined in vitro in the housefly (23,... 

The pathway The first committed step in fatty acid biosynthesis is the carboxylation of acetyl CoA to form malonyl CoA which is catalyzed by the biotin-containing enzyme acetyl CoA carboxylase. Acetyl CoA and malonyl CoA are then converted into their ACP derivatives. The elongation cycle in fatty acid synthesis involves four reactions condensation of acetyl-ACP and malonyl-ACP to form acetoacetyl-ACP releasing free ACP and C02, then reduction by NADPH to form D-3-hydroxybutyryl-ACP, followed by dehydration to crotonyl-ACP, and finally reduction by NADPH to form butyryl-ACP. Further rounds of elongation add more two-carbon units from malonyl-ACP on to the growing hydrocarbon chain, until the C16 palmitate is formed. Further elongation of fatty acids takes place on the cytosolic surface of the smooth endoplasmic reticulum (SER). 

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