Prenyl lipid formation in spinach chloroplasts and in a cell-free system of Synechococcus (Cyanobacteria): polyprenols, chlorophylls, and fatty acid prenyl esters

Abstract

Isolated chloroplasts from spinach leaf cells, chloroplast subfractions, and a cell-free system of the cyanobacterium Synechococcus CCAP 6312 incorporated [1-(14)C]isopentenyl pyrophosphate in high yields into prenyl lipids. Products were polyprenols (C20, C45) chlorophylls, quinoid compounds, and fatty acid prenyl esters; prenyl pyrophosphates occurred in trace amounts, and carotenes were only formed to a limited extent in the Synechococcus system. The formation of fatty acid prenyl esters, which is described here for the first time, was found to occur in two different ways in the chloroplast system; by an acyl-CoA: polyprenol acyltransferase reaction associated with the envelope membranes and by a transesterification reaction from chlorophyll associated with the thylakoids. Endogenous fatty acid prenyl esters made up about 3% by weight of total lipids in spinach chloroplasts and were also found to be natural constituents of the cyanobacterial cells.