Octadecenoate. Acid moiety of some ester substrate. Can be the product of hydrolysis of an ester and act as an inhibitor of the enzyme and be found in the active site in some structuresOleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. It is a monounsaturated omega-9 fatty acid, abbreviated as 18:1 cis-9. It has the formula CH3(CH2)7CH=CH(CH2)7COOH. The name derives from the Latin word oleum, which means oil. It is the most common fatty acid in nature