<p>This protein is has been characterised as both a phosphoserine phosphatase and a phosphoserine:homoserine phosphotransferase [<cite idref="PUB00015488"/>]. In <taxon tax_id="287">Pseudomonas aeruginosa</taxon>, where the characterisation was done, a second phosphoserine phosphatase (SerB) and a second homoserine kinase (thrB) are found, but in <taxon tax_id="833">Fibrobacter succinogenes</taxon> neither are present. </p>