title: Surface loops of extracellular phospholipase A(1) determine both substrate specificity and preference for lysophospholipids.
abstract: Members of the pancreatic lipase family exhibit both lipase activity toward triacylglycerol and/or phospholipase A(1) (PLA(1)) activity toward certain phospholipids. Some members of the pancreatic lipase family exhibit lysophospholipase activity in addition to their lipase and PLA(1) activities. Two such enzymes, phosphatidylserine (PS)-specific PLA(1) (PS-PLA(1)) and phosphatidic acid (PA)-selective PLA(1)α (PA-PLA(1)α, also known as LIPH) specifically hydrolyze PS and PA, respectively. However, little is known about the mechanisms that determine their substrate specificities. Crystal structures of lipases and mutagenesis studies have suggested that three surface loops, namely, β5, β9, and lid, have roles in determining substrate specificity. To determine roles of these loop structures in the substrate recognition of these PLA(1) enzymes, we constructed a number of PS-PLA(1) mutants in which the three surface loops are replaced with those of PA-PLA(1)α. The results indicate that the surface loops, especially the β5 loop, of PA-PLA(1)α play important roles in the recognition of PA, whereas other structure(s) in PS-PLA(1) is responsible for PS preference. In addition, β5 loop of PS-PLA(1) has a crucial role in lysophospholipase activity toward lysophosphatidylserine. The present study revealed the critical role of lipase surface loops, especially the β5 loop, in determining substrate specificities of PLA(1) enzymes.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Tohoku University, Miyagi, 980-8578 Japan.
authors.forename: Naoaki
authors.initials: N
authors.lastname: Arima
authors.affiliation: Graduate School of Pharmaceutical Sciences, Tohoku University, Miyagi, 980-8578 Japan.
authors.forename: Asuka
authors.initials: A
authors.lastname: Inoue
authors.affiliation: Graduate School of Pharmaceutical Sciences, Tohoku University, Miyagi, 980-8578 Japan; PRESTO, Japan Science and Technology Corporation, Tokyo 102-0076, Japan.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Makide
authors.affiliation: Department of Structural Biology, School of Pharmacy, Iwate Medical University, Iwate 028-3694, Japan.
authors.forename: Takamasa
authors.initials: T
authors.lastname: Nonaka
authors.affiliation: Graduate School of Pharmaceutical Sciences, Tohoku University, Miyagi, 980-8578 Japan; CREST, Japan Science and Technology Corporation, Tokyo 102-0076, Japan. Electronic address: jaoki@m.tohoku.ac.jp.
authors.forename: Junken
authors.initials: J
authors.lastname: Aoki
mesh_terms: D015153:Blotting, Western; D002460:Cell Line; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008246:Lysophospholipids / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D054466:Phospholipases A1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013379:Substrate Specificity
chemical_list: D008246:Lysophospholipids; D010712:Phosphatidic Acids; D010718:Phosphatidylserines; C025059:lysophosphatidylserine; D054466:Phospholipases A1; C032881:lysophosphatidic acid