Membrane-Bound Enzymes in Plant Sterol Biosynthesis

Abstract

The basic pattern of sterol biosynthesis in plants is similar to that involved in cholesterol biosynthesis in mammals, but there are important differences of detail. There are also additional reactions in plants such as alkylation at C-24, glucosylation at C-3, and side-chain desaturation, most frequently at C-2. Sterol biosynthesis in mammals has been studied at the enzyme level to a much greater extent than has phytosterol biosynthesis. Part of the reason is that plant enzymes, particularly those in higher plants, are notoriously difficult to deal with (Loomis, 1973). However, reliable information is accumulating, and in presenting the evidence for the involvement of membrane-bound enzymes in sterol biosynthesis in plants one realizes that the foundations for future developments, not only in enzymology but in studies on the control of synthesis, are now reasonably well established.