Synthesis of prenyl lipids in cells of spinach leaf: Compartmentation of enzymes for formation of isopentenyl diphosphate

Abstract

Purified spinach chloroplasts incorporate [1‐14C]isopentenyl diphosphate into prenyl lipids in high yields. The immediate biosynthetic precursors of isopentenyl diphosphate (hydroxymethylglutaryl‐CoA, mevalonate, mevalonate‐5–phosphate, mevalonate‐5‐diphosphate), on the other hand, are not accepted as substrates and the corresponding enzymes hydroxymethylglutaryl‐CoA reductase, mevalonate kinase, phosphomevalonate kinase, and diphosphomevalonate decarboxylase are not present in the organelles. These enzymes can only be detected in a membrane‐bound form at the endoplasmic reticulum (hydroxymethylglutaryl‐CoA reductase) and as soluble activities in the cytoplasm. The concept is developed that isopentenyl diphosphate is formed in the cytoplasm as a ‘central intermediate’ and is distributed then to other cellular compartments (endoplasmic reticulum, plastids, mitochondria) for further biosynthetic utilization. Copyright © 1984, Wiley Blackwell. All rights reserved