Human L-3-phosphoserine phosphatase: Sequence, expression and evidence for a phosphoenzyme intermediate

We report the sequence of the cDNA encoding human L-3-phosphoserine phosphatase, The encoded polypeptide contains 225 residues and shows 30% sequence identity with the Escherichia coli enzyme, The human protein was expressed in a bacterial expression system and purified, Similar to known L-3-phosphoserine phosphatases, it catalyzed the Mg2+-dependent hydrolysis of L-phosphoserine and an exchange reaction between L-serine and L-phosphoserine. In addition we found that the enzyme was phosphorylated upon incubation with L-[P-32]phosphoserine, which indicates that the reaction mechanism proceeds via the formation of a phosphoryl-enzyme intermediate, The sensitivity of the phosphoryl-enzyme to alkali and to hydroxylamine suggests that an aspartyl- or a glutamyl-phosphate was formed, The nucleotide sequence of the cDNA described in this article has been deposited in the EMBL data base under accession number Y10275. (C) 1997 Federation of European Biochemical Societies.