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 ph osphatase, 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+-depende nt hydrolysis of L-phosphoserine and an exchange reaction between L-se rine and L-phosphoserine. In addition we found that the enzyme was pho sphorylated upon incubation with L-[P-32]phosphoserine, which indicate s that the reaction mechanism proceeds via the formation of a phosphor yl-enzyme intermediate, The sensitivity of the phosphoryl-enzyme to al kali and to hydroxylamine suggests that an aspartyl- or a glutamyl-pho sphate was formed, The nucleotide sequence of the cDNA described in th is article has been deposited in the EMBL data base under accession nu mber Y10275. (C) 1997 Federation of European Biochemical Societies.