Genetic Analysis Using Vitamin B 6 Antagonist 4-Deoxypyridoxine Uncovers a Connection between Pyridoxal 5'-Phosphate and Coenzyme A Metabolism in Salmonella enterica

• Published in: Journal of bacteriology 2022-03, Vol.204 (3), p.e0060721
• Main Authors: Vu, Huong N, Downs, Diana M
• Format: Article
• Language: English
• Subjects: Coenzyme A; NAD; Phosphates; Pyridoxal Phosphate - metabolism; Pyridoxine - analogs & derivatives; Salmonella enterica - genetics; Salmonella enterica - metabolism; Salmonella typhimurium - metabolism; Thiamine; Vitamin B 6 - metabolism; Vitamins
• ISSN: 0021-9193; 1098-5530
• DOI: 10.1128/jb.00607-21

Pyridoxal 5'-phosphate (PLP) is an essential cofactor for organisms in all three domains of life. Despite the central role of PLP, many aspects of vitamin B metabolism, including its integration with other biological pathways, are not fully understood. In this study, we examined the metabolic perturbations caused by the vitamin B antagonist 4-deoxypyridoxine (dPN) in a mutant of Salmonella enterica serovar Typhimurium LT2. Our data suggest that PdxK (pyridoxal/pyridoxine/pyridoxamine kinase [EC 2.7.1.35]) phosphorylates dPN to 4-deoxypyridoxine 5'-phosphate (dPNP), which in turn can compromise the biosynthesis of PLP. The data are consistent with the hypothesis that accumulated dPNP inhibits GlyA (serine hydroxymethyltransferase [EC 2.1.2.1]) and/or GcvP (glycine decarboxylase [EC 1.4.4.2]), two PLP-dependent enzymes involved in the generation of one-carbon units. Our data suggest that this inhibition leads to reduced flux to coenzyme A (CoA) precursors and subsequently decreased synthesis of CoA and thiamine. This study uncovers a link between vitamin B metabolism and the biosynthesis of CoA and thiamine, highlighting the integration of biochemical pathways in microbes. PLP is a ubiquitous cofactor required by enzymes in diverse metabolic networks. The data presented here expand our understanding of the toxic effects of dPN, a vitamin B antagonist that is often used to mimic vitamin B deficiency and to study PLP-dependent enzyme kinetics. In addition to PLP biosynthesis, we define a metabolic connection between vitamin B metabolism and synthesis of thiamine and CoA. This work provides a foundation for the use of dPN to study vitamin B metabolism in other organisms.