Isopentenyl diphosphate isomerase deficiency in Synechocystis sp strain PCC6803

Isopentenyl diphosphate isomerase (IPP isomerase) in many organisms and in plastids is central to isoprenoid synthesis and involves the conversion bet ween IPP and dimethylallyl diphosphate (DMAPP). It is shown that Synechocys tis PCC6803 is deficient in IPP isomerase activity, consistent with the abs ence in its genome of an obvious homologue for the enzyme. Incorporation of [1-C-14]IPP in cell extracts, primarily into C-20, occurs only upon primin g with DMAPP in Synechocystis PCC6803 and in Synechoccus PCC7942. Isoprenoi d synthesis in these cyanobacteria does not appear to involve interconversi on of IPP and DMAPP, raising the possibility that they are not within the p lastid evolutionary lineage. (C) 2000 Federation of European Biochemical So cieties.