Growth Retardant - Induced Inhibition of Neutral Terpene Biosynthesis Using Plant and Animal Cell-Free Systems1

Abstract

Abstract Nine plant growth retardants were tested for their ability to inhibit neutral terpene biosynthesis by enzymes in cell-free extracts from rat liver, iris (Iris hollandica Hoog. cv. ‘Wedgwood’) sprouts, and castor bean (Ricinus communis L. cv. ‘Baker Hybrid 66’) seeds. Succinic acid 2,2-dimethylhydrazide (SADH), α-cyclopropyl-α (4-methoxyphenyl)-5-pyrimidine-methanol (A-Rest), n,n-dimethylmorpholinium chloride (BAS 0660-W), and 2-chloroethyl trimethyl-ammonium chloride (Cycocel) showed little or no inhibitory effects regardless of concentration or the test system used. Using rat liver enzymes, 2-isopropyl-4-dimethylamino-5-methylphenyl-l-piperidine-carboxy-late methyl chloride (AMO-1618) at 0.01 mM, inhibited cholesterol biosynthesis after the farnesyl-pyrophosphate step but had no inhibitory effect in the bean and iris cell-free systems. CHE-9064 (structure not released), Phosfon-D (2,4-dichlorobenzyl tributylphosphonium chloride) and 3-trifluoromethyl sulfonamido-p-acetotoluidide (Sustar) also inhibited cholesterol biosynthesis in rat liver enzymes at concentrations as low as 0.01 mM while 5-chloro-2-thenyl-tri-n-butyl chloride (CHE-8728) lost its effectiveness at concentrations below 0.1 mM. In the iris system, CHE-8728, Phosfon-D and Sustar inhibited cholesterol and farnesol production at 0.1 mM but were ineffective at lower concentrations. With the castor bean system, Sustar was the only retardant to inhibit terpene biosynthesis. Results indicate that CHE-8728, CHE-9064, Phosfon-D, and Sustar inhibit the terpene biosynthetic pathway prior to the formation of the farnesyl-pyrophosphate (rat liver and iris system) or geranylgeranyl-pyrophosphate (castor bean system).