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| Version | Summary | Created by | Modification | Content Size | Created at | Operation |
|---|---|---|---|---|---|---|
| 1 | Shun Yaginuma | -- | 1640 | 2022-04-25 15:19:04 | | | |
| 2 | Camila Xu | + 322 word(s) | 1962 | 2022-04-26 03:54:58 | | | | |
| 3 | Camila Xu | Meta information modification | 1962 | 2022-04-26 04:05:41 | | |
Phospholipase A1 (PLA1) is an enzyme that cleaves an ester bond at the sn-1 position of glycerophospholipids, producing a free fatty acid and a lysophospholipid.
Figure 1. Structures of glycerolipids and their metabolic enzymes. (A) Glycerophospholipids (GPL) and phospholipases. GPLs are composed of a polar head group (six major classes), a glycerol backbone and fatty acid moieties (esterified at the sn-1 and sn-2 positions). Phospholipase A1 (PLA1) hydrolyzes a fatty acid at the sn-1 position, generating sn-2-acyl-1-lyso-phospholipids (sn-2-acyl LPLs), while phospholipase A2 (PLA2) hydrolyzes a fatty acid at the sn-2 position generating sn-1-acyl-2-lyso-phospholipids (sn-1-acyl LPLs). Phospholipase B (PLB) hydrolyzes a fatty acid at both sn-1 and sn-2 positions. LysoPLA hydrolyzes a fatty acid of sn-2-acyl LPLs and sn-1-acyl LPLs, generating glycerophosphate compounds. (B) Triacylglycerol (TAG) has three fatty acids at the sn-1, sn-2 and sn-3 positions of glycerol backbone, diacylglycerol (DAG) has two fatty acids and monoacylglycerol (MAG) has one fatty acid. TAG lipase hydrolyzes a fatty acid of TAG, generating sn-1, 2, sn-2, 3 or sn-1, 3-diacylglycerols (DAGs). DAG lipase hydrolyzes a fatty acid of DAG and MAG lipase hydrolyzes a fatty acid of MAG.
Figure 2. Fatty acid remodeling reactions of GPLs. Glycerophospholipids (GPL) in the cells are constantly subjected to two kinds of fatty acid hydrolyzing reactions mediated by phospholipase A1 (PLA1) and phospholipase A2 (PLA2), resulting in the production of 2-acyl-1-lysophospholipid (sn-2 LPL) and 1-acyl-2-lysophospholipid (sn-1 LPL). The LPLs thus produced are further subjected to acylation reactions to re-form the GPLs. Several kinds of lysophospholipid acyltransferases (LPLAT) are responsible for the introduction of fatty acids to lysophospholipids. By these sequential GPL remodeling reactions, the fatty acids of GPLs are constantly replaced.
Figure 3. Physiological roles of extracellular PLA1s. (A) PS-PLA1 and mPA-PLA1α serve as producing enzymes for lysophospholipid mediators. PS-PLA1 has a strict substrate specificity in that it only acts on serine containing GPLs such as phosphatidylserine (PS) and lysophosphatidylserine (LysoPS). LysoPS then acts on GPCR-type LysoPS receptors. Three such LysoPS receptors have been identified. These include LPSR1/GPR34, LPSR2/P2Y10, and LPSR3/GPR174. mPA-PLA1α acts on PA in a specific manner and produces sn-2 LPA, which then acts on GPCR-type LPA receptors, LPAR1-LPAR6 evoking various biological responses. (B) Pancreatic lipase (PL) is secreted from the pancreas into the lumen of the intestine, where it, with the aid of bile acids, hydrolyzes the fatty acids of triacylglycerol (TAG) and GPLs in the digestive juice yielding diacylglycerol (DAG), monoacylglycerol (MAG) and fatty acids. The liberated fatty acids are absorbed by intestinal cells as nutrients. (C) Lipoprotein lipase (LPL), hepatic lipase (HL), and endothelial lipase (EL), which are mainly present in the blood, are associated with endothelial cell surfaces in adipose tissues (LPL), heart (LPL), liver (HL) and various tissues. These lipases have both TAG lipase and PLA1 activities. They hydrolyze fatty acids of TAG and GPLs present in the circulating lipoproteins such as low-density lipoproteins (LDL) and high-density lipoproteins (HDL), yielding diacylglycerol (DAG), monoacylglycerol (MAG), lysophospholipids (LPL) and fatty acids. The free fatty acids are absorbed by corresponding cells for energy source and storage of neutral lipids.| Primary Name | Other Name | Human Gene | Substrate | Reaction Mediated | PDB ID (H: Human, R: Rat) |
Ref. | |
|---|---|---|---|---|---|---|---|
| extracellular PLA1s | PS-PLA1 | PLA1A | PLA1A | PS | Producing enzyme for bioactive lysophospholipid, LysoPS | - | [7][8] |
| PA-PLA1α | LIPH, mPA-PLA1α | LIPH | PA | Producing enzyme for bioactive lysophospholipid, LPA | - | [4][9] | |
| lipoprotein lipase | LPL, LIPD | LIPD | TAG, PL | TAG lipase and PLA1 activity | H: 6E7K, 6OAU, 6OAZ, 6OB0, 6WN4 | [10] | |
| hepatic lipase | HL, LIPC | LIPC | TAG, PL | TAG lipase and PLA1 activity | - | [10] | |
| endothelial cell-derived lipase | EDL, EL, LIPG | LIPG | PL | Predominant PLA1 activity | - | ||
| pacreatic lipase | PL, PNLIP | PNLIP | TAG, PL | TAG lipase and PLA1 activity | H: 1GPL, 1LPA, 1LPB, 1N8S | [11][12][13] | |
| pancreatic lipase-related protein 1 | PLRP1 | PLRP1 | TAG, PL | TAG lipase and PLA1 activity | H: 2PPL | ||
| pancreatic lipase-related protein 2 | PLRP2 | PLRP2 | TAG, PL | TAG lipase and PLA1 activity | H: 2OXE, 2PVS; R: 1BU8 | [11][13] | |
| intracellular PLA1s | PA-PLA1 | DDHD1, iPLA1α | DDHD1 | PL | PLA1 activity | - | [14][15] |
| KIAA0725p | DDHD2, iPLA1γ | DDHD2 | PL | PE, DAG, CL | - | [16][17][18] | |
| p125 | iPLA1β | P125 | n.d. | Enzymatic activity has not been detected | - | [19] | |
| PNPLA6 | iPLA2δ, NTE | PNPLA6 | PC, LPC | PLB, LysoPLA activity cleaving FAs at both sn-1 and sn-2 positions | - | [20][21][22] | |
| PNPLA7 | iPLA2θ, NRE | PNPLA7 | PC, LPC | PLB, LysoPLA activity cleaving FAs at both sn-1 and sn-2 positions | - | [23] | |
| PNPLA8 | iPLA2γ, Group VIB PLA2 | PNPLA8 | PC | PLB activity cleaving FAs at both sn-1 and sn-2 positions | - | [24][25] | |
| cPLA2α | PLA2G4A, Group IVA PLA2 | PLA2G4A | PL | PLB activity cleaving FAs at both sn-1 and sn-2 positions | H: 1BCI, 1CJY, 1RLW | [26] | |
| cPLA2β | PLA2G4B, Group IVB PLA2 | PLA2G4B | PL | PLB activity cleaving FAs at both sn-1 and sn-2 positions | - | [26][27] | |
| cPLA2ζ | PLA2G4F, Group IVF PLA2 | PLA2G4F | PL | PLB activity cleaving FAs at both sn-1 and sn-2 positions | - | ||
| PLA2G16 | Group XVI PLA2, PLAAT3, HRASLS3, H-Rev107 | PLA2G16 | PL | PLB activity cleaving FAs at both sn-1 and sn-2 positions | H: 2KYT, 4DOT, 4FA0, 4Q95, 7C3Z, 7C41 | [28] |
Figure 4. Structures of PLA1 molecules. 3D structures of three PLA1 family members (extracellular PLA1/lipase, cPLA2 and PLAAT family members) were shown. For extracellular PLA1/lipase family members, β5 and the β9 loops and the lid domain are shown in yellow, cyan and green, respectively. The three residues forming a catalytic triad (Ser, Asp and His) are described as sticks (red). For cPLA2 family members (cPLA2α, cPLA2β and cPLA2ζ), the conserved lipase motifs (GXSGX and DXG) are shown in red, and the two residues forming a catalytic dyad (Ser and Asp) are shown as sticks. For PLAAT3/PLA2G16, the three residues forming a catalytic triad (two histidines and cysteine) are shown as sticks (red). The structures without asterisk were acquired from RCSB Protein Data Bank. (Reference PDB IDs; PL (1LPB), LPL (6OB0), PLRP1 (2PPL), cPLA2α (1CJY), PLA2G16 (4DOT)). The predicted structures of lipases with asterisk were acquired from AlphaFold Protein Structure Database. All the structures were visualized using PyMOL software.