Castor Bean Lipase: Role of the Lipid Cofactor

There is characteristic visual change in the enzyme–substrate particles undergoing lipolysis catalyzed by castor bean lipase. The particles swell, become irregular in shape, and accumulate granular deposits. If the cofactor is not removed from the apoenzyme, these changes can be inhibited by poisoning the enzyme with mercuric chloride without affecting emulsification of the oil substrate, enzyme, and water. It appears that the enzyme is coalesced within the lipid substrate; the composition of this coalesced particle is determined by the relative amounts of enzyme and substrate and by the degree of dispersion. The reaction does not seem to take place solely on the surface, as previously thought.