Genetic and biochemical analyses of pantothenate biosynthesis in Escherichia coli and Salmonella typhimurium.
Pantothenate (pan) auxotrophs of Escherichia coli K-12 and Salmonella typhimurium LT2 were characterized by enzymatic and genetic analyses. The panB mutants of both organisms and the pan-6 ("panA") mutant of S. typhimurium are deficient in ketopantoate hydroxymethyltransferase, whereas the panC mutants lack pantothenate synthetase. panD mutants of E. coli K-12 were previously shown to be deficient in aspartate 1-decarboxylase. All mutants showed only a single enzyme defect. The finding that the pan-6 mutant was deficient in ketopantoate hydroxymethyltransferase indicates that the genetic lesion is a panB allele. The pan-6 mutant therefore is deficient in the utilization of alpha-ketoisovalerate rather than the synthesis of alpha-ketoisovalerate, as originally proposed. The order of the pan genes of E. coli K-12 was determined by phage P1-mediated three-factor crosses. The clockwise order was found to be aceF panB panD panC tonA on the genetic map of E. coli K-12. The three-factor crosses were greatly facilitated by use of a closely linked Tn10 transposon as the outside marker. We also found that supplementation of E. coli K-12 auxotrophs with a high concentration of pantothenate or beta-alanine increased the intracellular coenzyme A level two- to threefold above the normal level. Supplementation with pantoate or ketopantoate resulted in smaller increases.
D002262:Carboxy-Lyases / Q000235:genetics; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D003065:Coenzyme A / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial; D019877:Hydroxymethyl and Formyl Transferases; D010205:Pantothenic Acid / Q000096:biosynthesis* / Q000235:genetics; D010453:Peptide Synthases / Q000235:genetics; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism*; D014166:Transferases
D010205:Pantothenic Acid; D014166:Transferases; D019877:Hydroxymethyl and Formyl Transferases; C021477:3-methyl-2-oxobutanoate hydroxymethyltransferase; D002262:Carboxy-Lyases; C019747:aspartate 4-decarboxylase; D010453:Peptide Synthases; C022318:pantothenate synthetase; D003065:Coenzyme A