BCH 609 Plant Biochemistry

EXAM II September 7, 2000

Deane Falcone

1. Much attention has been given to the enzyme 3-hydroxy 3-methylglutaryl CoA reductase (HMGR) in plants because of the important position it occupies in the biosynthetic pathway leading to sterol biosynthesis in animal cells. However, results have either been mixed or confusing regarding the importance of this enzymatic step in plants primarily because of the apparent lack of involvement observed in the biosynthesis of a variety of (i.e., some, but not all) isoprenoid-derived products. Discuss why HMGR does not apparently play a central role in the formation of all isoprenoids in plants. (8 points)

2. A characteristic of products derived from “secondary” pathways is the immense diversity in the structures of products formed. The isoprenoid pathway in particular is responsible for a large number of such compounds. Explain how different reaction products can be derived from the same substrate, farnesylpyrophosphate (FPP) in the formation of sesquiterpenoids in plants. (6 points)