Solubilization, partial purification, and characterization of a fatty aldehyde decarbonylase from a higher plant, Pisum sativum

Enzymatic decarbonylation of fatty aldehydes generates hydrocarbons. The pa rticulate enzyme that catalyzes the decarbonylation has not been solubilize d and purified from any organism but a green alga. Here we report the solub ilization, 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 P-o ctyl glucoside and partially purified. SDS-PACE showed a major protein band at 67 kDa. Rabbit antibodies raised against this protein specifically cros s-reacted with the 67-kDa protein in solubilized microsomal preparations; a nti-ribulose bisphosphate carboxylase cross-reacted only with the 49-kDa la rge subunit of the carboxylase, but not with any protein near 67 kDa, showi ng the absence of any contamination from cross-linked small-large subunit o f the carboxylase found in the green algal enzyme preparation. Anti-67-kDa protein antibodies inhibited decarbonylation catalyzed by the enzyme prepar ations, showing that this protein represents the decarbonylase. Decarbonyla se activity of the purified enzyme required phospholipids for activity; pho sphatidylcholine was the preferred lipid although phosphatidylserine and ph osphatidylethanolamine could substitute less effectively. Half-maximal acti vity was observed at 40 mu M octadecanal. The purified enzyme produced alka ne and CO and was inhibited by O-2, NADPH, and DTE. Metal ion chelators sev erely inhibited the enzyme and Cu2+ fully restored the enzyme activity. Pur ified enzyme preparations consistently showed the presence of Cu, and coppe r protoporphyrin IX catalyzed decarbonylation. These results suggest that t his higher plant enzyme probably is a Cu enzyme unlike the green algal enzy me that was found to have Co. (C) 2000 Academic Press.