| By DNA sequencing of an 8 . 9 kb BamHI fragment , 7 genes encoding geranylgeranyl diphosphate synthase ( GGDPS ) , mevalonate kinase ( MK ) , mevalonate diphosphate decarboxylase ( MDPD ) , phosphomevalonate kinase ( PMK ) , isopentenyl diphosphate ( IPP ) isomerase , HMG CoA reductase , and HMG CoA synthase were suggested to exist in that order . ^^^ |