ACID LIPASES OF CASTOR BEAN

The acid lipase of the castor bean is present in the dormant seed. It is extracted from the fat pad obtained by centrifuging a macerate of the seed in pH 7.0 buffer containing cysteine and ethylene diaminetetraacetic acid. The pH optimum of the enzyme is 4.2; it is rather heat-stable, and is inhibited by mercurials and sulfhydryl reagents. Maximum hydrolysis of saturated triglycerides occurs with fatty acids of chain length C4 to C8; unsaturated C18 triglycerides are hydrolyzed at a slightly lower rate. This lipase is a three-component system consisting of the apoenzyme, a lipid cofactor (a cyclic tetramer of ricinoleic acid), and a protein activator (a small, heat-stable glycoprotein which appears to be related to some of the castor allergens). Maximum lipolysis requires all three components. Lipase activity is associated with the spherosomes, the subcellular site of oil storage in the endosperm. © 1969 American Oil Chemists' Society.