Purine limitation prevents the exogenous pyridoxal 5'-phosphate accumulation of mutants.

Unlabelled: YggS belongs to the highly conserved pyridoxal 5'-phosphate (PLP) binding protein family (COG0325) that is found in all domains of life. Though no precise biochemical activity or molecular mechanism has been determined for this protein, an involvement in vitamin B homeostasis has been demonstrated in multiple organisms. In , loss of YggS results in altered B vitamer pools, including an accumulation of PLP in the growth medium.