Role of the conserved pyridoxal 5ʹ-phosphate-binding protein YggS/PLPBP in vitamin B6and amino acid homeostasis

The YggS/PLPBP protein (also called COG0325 or PLPHP) is a conserved pyridoxal 5ʹ-phosphate (PLP)-binding protein present in all 3 domains of life. Recent studies have demonstrated that disruption or mutation of this protein has multifaceted effects in various organisms, including vitamin B6-dependent epilepsy in humans. In Escherichia coli, disruption of this protein—encoded by yggS—perturbs Thr-Ile/Val metabolism, one-carbon metabolism, coenzyme A synthesis, and vitamin B6homeostasis. This protein is critical for maintaining low levels of pyridoxine 5ʹ-phosphate (PNP) in various organisms. In the yggS-deficient E. colistrain, inhibition of PLP-dependent enzymes, such as the glycine cleavage system by PNP, is the root cause of metabolic perturbation. Our data suggest that the YggS/PLPBP protein may be involved in the balancing of B6vitamers by mediating efficient turnover of protein-bound B6vitamers. This paper reviews recent findings on the function of the YggS/PLPBP protein.Graphical AbstractRole of YggS/PLPBP protein in vitamin B6and amino acid homeostasis.