Biosynthesis of allylic isoprenoid pyrophosphates by an enzyme preparation from the flavedo of Citrus paradisii

Abstract

Abstract A cell-free system obtained from Citrus paradisii flavedo transformed mevalonic acid into mono- and sesquiterpenoids of E - and Z -conformation. The enzyme system required bivalent metal ions and the presence of sulfhydryl groups. IPP isomerase activity (EC 5.3.3.2) was independent of metal ions and almost insensitive to sulfhydryl group reagents, while prenyltransferase (EC 2.5.1.1) was inactivated by DTNB and required bivalent metals for activity. The nature of the metal ion defined the stereochemistry of the products formed by prenyltransferase. The ratio of E–Z farnesylpyrophosphates was 3:1. This Citrus species could, therefore, be a good starting material for the study of the stereochemistry of the enzymes forming E and Z sesquiterpenoids.