The Metabolism of Isoprenoid Precursors in a Plant System

Abstract

The mechanism of synthesis of branched-chain compounds from acetate has been investigated with the aid of an enzyme system prepared from flax seedlings. It has been shown that this enzyme system is capable of activating acetate to acetyl-CoA and that the acetyl-CoA thus formed is converted to derivatives of [beta]-hydroxy-[beta]-methyl glutarate and [beta]-mettiyl crotonate. The synthesis of [beta]-hydroxy-[beta]-methyl glutarate appears to take place through the acetylation of acetoacetate. [beta]-Methyl crotonate is activated by the enzyme preparation in the presence of ATP and CoA and is converted with the uptake of CO2 to [beta]-hydroxy-[beta]-methyl glutarate. The latter can be further degraded to acetoacetate and acetyl-CoA. The sequence of reactions studied is of interest in relation to the role of [beta]-methyl crotonate in the biosynthesis of rubber, steroids, and other isoprenoid compounds.