title: Catalytic residues of group VIB calcium-independent phospholipase A2 (iPLA2gamma).
abstract: Although human group VIB calcium-independent phospholipase A(2) (iPLA(2)gamma) contains the lipase-consensus sequence Gly-Xaa-Ser-Xaa-Gly in the C-terminal half, its overall sequence exhibits a week similarity to those of other PLA(2)s, and thus no information on the catalytic site has been available. Here we show that the C-terminal region of human iPLA(2)gamma is responsible for the enzymatic activity. Comparison of this catalytic domain with those of the mouse homologue, human cytosolic PLA(2) (cPLA(2)), and the plant PLA(2) patatin reveals that an amino acid sequence of a short segment around Asp-627 of iPLA(2)gamma is conserved among these PLA(2)s, in addition to the Ser-483-containing lipase motif; the corresponding serine and aspartate in cPLA(2) and patatin are known to form a catalytic dyad. Since substitution of alanine for either Ser-483 or Asp-627 results in a loss of the PLA(2) activity, we propose that Ser-483 and Asp-627 of human iPLA(2)gamma constitute an active site similar to the Ser-Asp dyad in cPLA(2) and patatin.
authors.affiliation: Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Haruki
authors.initials: H
authors.lastname: Tanaka
authors.forename: Reiko
authors.initials: R
authors.lastname: Minakami
authors.forename: Hideki
authors.initials: H
authors.lastname: Kanaya
authors.forename: Hideki
authors.initials: H
authors.lastname: Sumimoto
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000596:Amino Acids / Q000737:chemistry*; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002384:Catalysis; D002522:Chlorocebus aethiops; D017124:Conserved Sequence; D004789:Enzyme Activation; D054522:Group VI Phospholipases A2; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010741:Phospholipases A / Q000737:chemistry* / Q000378:metabolism*; D054467:Phospholipases A2; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
chemical_list: D000596:Amino Acids; D010741:Phospholipases A; D054522:Group VI Phospholipases A2; C516475:PLA2G6 protein, human; D054467:Phospholipases A2; C516476:Pla2g6 protein, mouse