title: The inositol polyphosphate 5-phosphatases and the apurinic/apyrimidinic base excision repair endonucleases share a common mechanism for catalysis.
abstract: Inositol polyphosphate 5-phosphatases (5-phosphatase) hydrolyze the 5-position phosphate from the inositol ring of phosphatidylinositol-derived signaling molecules; however, the mechanism of catalysis is only partially characterized. These enzymes play critical roles in regulating cell growth, apoptosis, intracellular calcium oscillations, and post-synaptic vesicular trafficking. The UCLA fold recognition server (threader) predicted that the conserved 300-amino acid catalytic domain, common to all 5-phosphatases, adopts the fold of the apurinic/apyrimidinic (AP) base excision repair endonucleases. PSI-BLAST searches of GENPEPT, using the amino acid sequence of AP endonuclease exonuclease III, identified all members of the 5-phosphatase family with highly significant scores. A sequence alignment between exonuclease III and all known 5-phosphatases revealed six highly conserved motifs containing residues that corresponded to the catalytic residues in the AP endonucleases. Mutation of each of these residues to alanine in the mammalian 43-kDa, or yeast Inp52p 5-phosphatase, resulted in complete loss of enzyme activity. We predict the 5-phosphatase enzymes share a similar mechanism of catalysis to the AP endonucleases, consistent with other common functional similarities such as an absolute requirement for magnesium for activity. Based on this analysis, functional roles have been assigned to conserved residues in all 5-phosphatase enzymes.
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: J C
authors.initials: JC
authors.lastname: Whisstock
authors.forename: S
authors.initials: S
authors.lastname: Romero
authors.forename: R
authors.initials: R
authors.lastname: Gurung
authors.forename: H
authors.initials: H
authors.lastname: Nandurkar
authors.forename: L M
authors.initials: LM
authors.lastname: Ooms
authors.forename: S P
authors.initials: SP
authors.lastname: Bottomley
authors.forename: C A
authors.initials: CA
authors.lastname: Mitchell
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019757:Carbon-Oxygen Lyases / Q000378:metabolism*; D002384:Catalysis; D018360:Crystallography, X-Ray; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D015723:Gene Library; D006801:Humans; D000072181:Inositol Polyphosphate 5-Phosphatases; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011487:Protein Conformation; D051381:Rats; D016415:Sequence Alignment
chemical_list: D043223:Deoxyribonuclease IV (Phage T4-Induced); D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; D019757:Carbon-Oxygen Lyases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase