The Pathway for CoQ Biosynthesis in Microorganisms and the Recent Progress in the Genetic Improvement of Microbial Strains for CoQ_(10) Production with the Aid of Molecular Biological Methods

The pathway for CoQ biosynthesis in microorganisms is a complex metabolic net.It is a conjunction of the following anabolic subnets:the biosynthetic pathways of shikimate,methionine(aspartate family),S-adenosylmethionine,isopentenyl diphosphate(IPP) and polyprenyl diphosphate(PPP) and the pathway for ring modification of ubiquinone.While bacteria derive the 4-hydroxybenzoate as the quinoid nucleus of the ubiquinone from the shikimate pathway and biosynthesize IPP from 2-C-Methyl-D-erythritol 4-phosphate pathway,eukaryotic microorganisms derive the 4-hydroxybenzoate or tyrosine as the quinoid nucleus of the ubiquinone from the shikimate pathway and biosynthesize IPP from the mevalonate pathway.CoQ10 has been used not only as a medicine but also as a food supplement because of its various physiological and biochemical activities(e.g.as an electron transporter in the respiratory chains of prokaryotes and eukaryotes and as an effective intracellular antioxidant,redox control of cell signaling and gene expression).Fermentation by microbes is the most effective way for CoQ10 production.The studies on the genetic improvement of the strains for CoQ10 production with the aid of molecular biological methods focused on four aspects:(1)Amplification of 1-deoxy-D-xyluose 5-phosphate synthase and chorismate pyruvate-lyase level increases CoQ10 production;(2)Cloning and expression of decaprenyl diphosphate synthase gene for production of CoQ10;(3)Cloning and expression of 4-hydroxybenzoate polyprenyltransferase gene for production of CoQ10;(4)Construction and introduction of multigene expression cassettes for production of CoQ10.