Solubilization, Partial Purification, and Characterization of a Fatty Aldehyde Decarbonylase from a Higher Plant, Pisum sativum

Enzymatic decarbonylation of fatty aldehydes generates hydrocarbons. The particulate enzyme that catalyzes the decarbonylation has not been solubilized and purified from any organism but a green alga. Here we report the solubilization, purification, and partial characterization of the decarbonylase from a higher plant. Decarbonylase from a particulate preparation from pea (Pisum sativum) leaves, enriched in decarbonylase, was solubilized with β-octyl glucoside and partially purified. SDS–PAGE showed a major protein band at 67 kDa. Rabbit antibodies raised against this protein specifically cross-reacted with the 67-kDa protein in solubilized microsomal preparations; anti-ribulose bisphosphate carboxylase cross-reacted only with the 49-kDa large subunit of the carboxylase, but not with any protein near 67 kDa, showing the absence of any contamination from cross-linked small–large subunit of the carboxylase found in the green algal enzyme preparation. Anti-67-kDa protein antibodies inhibited decarbonylation catalyzed by the enzyme preparations, showing that this protein represents the decarbonylase. Decarbonylase activity of the purified enzyme required phospholipids for activity; phosphatidylcholine was the preferred lipid although phosphatidylserine and phosphatidylethanolamine could substitute less effectively. Half-maximal activity was observed at 40 μM octadecanal. The purified enzyme produced alkane and CO and was inhibited by O2, NADPH, and DTE. Metal ion chelators severely inhibited the enzyme and Cu2+ fully restored the enzyme activity. Purified enzyme preparations consistently showed the presence of Cu, and copper protoporphyrin IX catalyzed decarbonylation. These results suggest that this higher plant enzyme probably is a Cu enzyme unlike the green algal enzyme that was found to have Co.