Alkane biosynthesis by decarbonylation of aldehydes catalyzed by a particulate preparation from Pisum sativum.
Mechanism of enzymatic conversion of a fatty acid to the corresponding alkane by the loss of the carboxyl carbon was investigated with particulate preparations from Pisum sativum. A heavy particulate preparation (sp. gr., 1.30 g/cm3) isolated by two density-gradient centrifugation steps catalyzed conversion of octadecanal to heptadecane and CO. Experiments with [1-3H,1-14C]octadecanal showed the stoichiometry of the reaction and retention of the aldehydic hydrogen in the alkane during this enzymatic decarbonylation. This decarbonylase showed an optimal pH of 7.0 and a Km of 35 microM for the aldehyde. This enzyme was severely inhibited by metal ion chelators and showed no requirement for any cofactors. Microsomal preparations and the particulate fractions from the first density-gradient step catalyzed acyl-CoA reduction to the corresponding aldehyde. Electron microscopic examination showed the presence of fragments of cell wall/cuticle but no vesicles in the decarbonylase preparation. It is concluded that the aldehydes produced by the acyl-CoA reductase located in the endomembranes of the epidermal cells are converted to alkanes by the decarbonylase located in the cell wall/cuticle region.
D000446:Aldehyde-Lyases / Q000302:isolation & purification / Q000378:metabolism*; D000447:Aldehydes / Q000378:metabolism*; D000473:Alkanes / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002499:Centrifugation, Density Gradient; D007887:Fabaceae; D005227:Fatty Acids / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010944:Plants / Q000201:enzymology*; D010946:Plants, Medicinal; D014316:Tritium
D000447:Aldehydes; D000473:Alkanes; D002250:Carbon Radioisotopes; D005227:Fatty Acids; D014316:Tritium; D000446:Aldehyde-Lyases; C043439:aldehyde decarbonylase