Study on the enzyme geranylgeraniol-18-hydroxylase in the biosynthesis of plaunotol in croton sublyratus Kurz.

Abstract

The activity of geranylgeraniol-18-hydroxylase, the enzyme catalyzes the C-18 hydroxylation of geranylgeraniol to plaunotol was discovered in the microsomal fraction prepared for Croton sublyratus Kurz. Leaves. This enzyme potentially involved in the final step of the biosynthesis of plaunotol, an antiulcerative constituent accumulated in this plant. Using geranylgeraniol as substrate and TLC-densitometer as enzymatic activity detector, the activity of geranylgeraniol-18-hydroxylase was found in the 20,000 g microsomal fraction. The formation of plaunotol was correlated with both incubation time and the amount of microsomal protein. The enzyme activity could be increased by adding NADPH or boiling the microsomal fraction. The pH optimum for the enzyme activity was 5.0. Observation of the microsomal fraction under electron microscope revealed the presence of particles with the diameter range between 20 nm to 60 nm. The discovery of this new enzyme activity has led to a possibility of using the enzyme for biotechnological application.