ABSTRACT
This chapter presents a summary of several aspects of the enzymology of phytosterol production. Studies on the enzymology of phytosterol synthesis have lagged behind similar enzymology studies performed with animals. However, there is now agronomic interest in elucidating the enzymology of phytosterol production. However, the enzymology to produce cholesterol is present in plants, as it is in fungi. The transformation of cycloartenol to stigmasterol has been mapped by the natural product approach and more recently by isolating microsome-bound enzymes that catalyze sterol transformations. The combination of mechanistic data on reaction course and on substrate binding studies show the stereoselectivity operating in phytosterol transformations in corn and sunflower. Additional evidence that favors the sterol methyl transferase (SMT) as the critical slow step in phytosterol transformation is based on the observations from sunflower and corn, which show that, of the enzymes that may act on cycloartenol, the SMT has the highest degree of sterol specificity and is a relatively slow-acting enzyme.
