Identification of YbhA as the pyridoxal 5'-phosphate (PLP) phosphatase in Escherichia coli: Importance of PLP homeostasis on the bacterial growth.

The gene ybhA of Escherichia coli encodes a phosphatase that has an in vitro specificity to dephosphorylate pyridoxal 5'-phosphate (PLP or vitamin B6), a co-factor for aminotransferases and other enzymes. In this study, we found that excess pyridoxal (PL) in a minimal medium resulted in excess PLP in vivo and growth inhibition, which was alleviated by YbhA overproduction. Conversely, the YbhA overproduction resulted in PLP shortage in vivo and the correlated reduction in growth rate, which was significantly negated by PL in the medium. In addition, the overproduction of a PL kinase, PdxK or PdxY, was inhibitory to cell growth only in the absence of the functional ybhA gene, and the growth defects were alleviated by casamino acids in the medium, which suggested that both the shortage of, and excess, PLP resulted in the disturbance of amino acid metabolism and cell growth, as revealed by a metabolome analysis.

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