Triacylglycerol lipase (type B carboxylestrase)

 

Catalyses the hydrolysis of all ester bonds in triglyceride and displays a high affinity for triolein. Member of the alpha-beta hydrolase superfamily.

 

Reference Protein and Structure

Sequence
P22394 UniProt (3.1.1.3) IPR002018 (Sequence Homologues) (PDB Homologues)
Biological species
Geotrichum candidum (Fungus) Uniprot
PDB
1thg - 1.8 ANGSTROMS REFINED STRUCTURE OF THE LIPASE FROM GEOTRICHUM CANDIDUM (1.8 Å) PDBe PDBsum 1thg
Catalytic CATH Domains
3.40.50.1820 CATHdb (see all for 1thg)
Click To Show Structure

Enzyme Reaction (EC:3.1.1.3)

triglyceride
CHEBI:17855ChEBI
+
water
CHEBI:15377ChEBI
→
diacylglycerol
CHEBI:18900ChEBI
+
hydron
CHEBI:15378ChEBI
+
fatty acid anion
CHEBI:28868ChEBI
Alternative enzyme names: GA 56, GEH, Meito MY 30, PPL, Takedo 1969-4-9, Tween hydrolase, Tweenase, Tweenesterase, Amano AP, Amano B, Amano CE, Amano CES, Amano P, Amno N-AP, Butyrinase, Cacordase, Capalase L, Glycerol ester hydrolase, Glycerol-ester hydrolase, Heparin releasable hepatic lipase, Hepatic lipase, Hepatic monoacylglycerol acyltransferase, Lipase, Lipazin, Liver lipase, Meito Sangyo OF lipase, Post-heparin plasma protamine-resistant lipase, Salt-resistant post-heparin lipase, Steapsin, Triacetinase, Triacylglycerol ester hydrolase, Tributyrase, Tributyrin esterase, Tributyrinase, Triglyceridase, Triglyceride hydrolase, Triglyceride lipase, Triolein hydrolase, Tween-hydrolyzing esterase,

Enzyme Mechanism

Introduction

This protein is a member of the alpha-beta hydrolase superfamily and is known to function via a Ser-His-Glu triad mechanism. Here the histidine of the triad activates the serine, which acts as a nucleophile, forming a covalent intermediate, which then collapses to eliminate the first product. Hydrolysis of the enzyme-substrate bond results in the release of the final product and regeneration of the active site.

Catalytic Residues Roles

UniProt PDB* (1thg)
Ala151 (main-N), Ala237 (main-N) Ala132A (main-N), Ala218A (main-N) Forms the oxyanion hole that stabilises the negatively charged intermediates and transition states formed during the course of the reaction. electrostatic stabiliser
Ser236 Ser217A Part of the Ser-His-Glu catalytic triad. Acts as a nucleophile. covalently attached, nucleofuge, nucleophile, proton acceptor, proton donor
Glu373 Glu354A Part of the Ser-His-Glu catalytic triad. Perturbates the pKa of the triad histidine. increase basicity, modifies pKa, electrostatic stabiliser
His482 His463A Part of the Ser-His-Glu catalytic triad. Acts as a general acid/base to activate the catalytic serine and water substrates. proton acceptor, proton donor
*PDB label guide - RESx(y)B(C) - RES: Residue Name; x: Residue ID in PDB file; y: Residue ID in PDB sequence if different from PDB file; B: PDB Chain; C: Biological Assembly Chain if different from PDB. If label is "Not Found" it means this residue is not found in the reference PDB.

Chemical Components

bimolecular nucleophilic addition, intermediate formation, overall reactant used, proton transfer, overall product formed, unimolecular elimination by the conjugate base, native state of enzyme regenerated, intermediate terminated

References

  1. Schrag JD et al. (1993), J Mol Biol, 230, 575-591. 1·8 Å Refined Structure of the Lipase from Geotrichum candidum. DOI:10.1006/jmbi.1993.1171. PMID:8464065.

Step 1. His463 acts as a general base activating the Ser217 hydroxyl group for nucleophilic attack on the carbonyl carbon of the ester bond. The third component of this catalytic triad- Glu354 acts to increase the basicity of the histidine. The oxyanion intermediate formed is stabilized by the amide groups of Ala132 and Ala218.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Ala132A (main-N) electrostatic stabiliser
Ala218A (main-N) electrostatic stabiliser
Glu354A electrostatic stabiliser, modifies pKa, increase basicity
Ser217A covalently attached
His463A proton acceptor
Ser217A proton donor, nucleophile

Chemical Components

ingold: bimolecular nucleophilic addition, intermediate formation, overall reactant used, proton transfer

Step 2. The tetrahedral intermediate collapses and diacylglycerol is eliminated.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Ser217A covalently attached
Ala132A (main-N) electrostatic stabiliser
Ala218A (main-N) electrostatic stabiliser
Glu354A electrostatic stabiliser
His463A proton donor

Chemical Components

overall product formed, proton transfer, ingold: unimolecular elimination by the conjugate base

Step 3. His463 activates water for nucleophilic attack and another oxyanion intermediate is formed.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Ser217A covalently attached
Ala132A (main-N) electrostatic stabiliser
Ala218A (main-N) electrostatic stabiliser
Glu354A electrostatic stabiliser, modifies pKa, increase basicity
His463A proton acceptor

Chemical Components

proton transfer, ingold: bimolecular nucleophilic addition

Step 4. The tetrahedral intermediate collapses and Ser217 is eliminated.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Ala132A (main-N) electrostatic stabiliser
Ala218A (main-N) electrostatic stabiliser
Glu354A electrostatic stabiliser
Ser217A proton acceptor, nucleofuge
His463A proton donor

Chemical Components

native state of enzyme regenerated, proton transfer, intermediate terminated, ingold: unimolecular elimination by the conjugate base, overall product formed
Download: Image, Marvin File

Step 1. His463 acts as a general base activating the Ser217 hydroxyl group for nucleophilic attack on the carbonyl carbon of the ester bond. The third component of this catalytic triad- Glu354 acts to increase the basicity of the histidine. The oxyanion intermediate formed is stabilized by the amide groups of Ala132 and Ala218.

Step 2. The tetrahedral intermediate collapses and diacylglycerol is eliminated.

Step 3. His463 activates water for nucleophilic attack and another oxyanion intermediate is formed.

Step 4. The tetrahedral intermediate collapses and Ser217 is eliminated.

Products.

Contributors

Christian Drew, Craig Porter, Gemma L. Holliday, James Willey