New simplified variant codes (first position): A 9 De novo synthesis from Aspartate, and complete universal pathway B 7 De novo synthesis from Aspartate, and incomplete universal pathway, possible pathway sharing as in Buchnera C 5 No de novo synthesis, salvage of pantothenate via universal pathway D 3 No de novo synthesis, salvage of pantothenate via pantetheine shunt E 1 Salvage of dephospho-CoA -1 1 Salvage of CoA (In some species individual roles may be missing)
New variant codes to reflect knowledge in archaea: F - full archaeal version de novo + universal (Source of b-Ala in most cases is to be defined, AspDC is present in severeal species as a clear case of HGT from bacteria). F.y - missing KPHMT; (F.x - something else is missing) G- archaeal version of salvage (not fully clear)
Coenzyme A (CoA) is a universal and indispensable co-factor involved with many central metabolic processes, including fatty acid metabolism, TCA, etc. Many free-living bacteria, fungi and plants are capable of de novo CoA biosynthesis via a committed precursor pantothenate (vitamin B5), whereas animals and a number of bacterial pathogens are dependent on consumption of exogenous pantothenate. Pantothenate is converted to CoA via a universal five-step pathway.Bacterial genes encoding all of the enzymes in this pathway (coaA through coaE) were identified and characterized in E.coli. All of these genes are indispensable for cell growth and survival, since most bacteria are impermeable for CoA or any of its phosphorylated intermediates (with the exception of some intracellular pathogens, such as Chlamydia spp). All eukaryotic genes involved with CoA universal pathway have been recently elucidated.
The current picture of the CoA biosynthetic pathway reveals a pronounced conservation of its enzymatic components across taxons. At the same time, significant variations are observed at the level of individual enzymes, including non-orthologous gene displacements, domain fusions and what are likely to be lateral gene transfer events. Most variations are observed for pantothenate kinase. Eg, in Staphylococci and Enterococci a bacterial coaA gene is replaced by a eukaryotic-like form, suggesting a possible horizontal gene transfer. The last enzyme in the pathway (DPCK) is conserved in all bacteria and eukarya, but it remains a missing gene in archaea. More details about the subsystem variants, key references etc are provided within teh Notes section.
For more information, please check out the description and the additional notes tabs, below
The biosynthesis of coenzyme A in bacteria. Begley TP Vitamins and hormones 2001