Enzyme - Phospholipase A(1)

Alternative Name(s)
  • Phospholipase A1.

Catalytic Activity

1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 2-acyl-sn-glycero-3-phosphocholine + a fatty acid + H(+)



Reaction Mechanism

    The outer membrane phospholipase A (OMPLA) is an integral membrane enzyme present in the outer membrane of Gram-negative bacteria. It catalyses the hydrolysis of acylester bonds in phospholipids. The physiological function of OMPLA is still not known.

    The mechanism of OMPLA is analogous to that of serine hydrolases. His162 acts as a base to deprotonate the side chain of Ser164 to allow its nucleophilic attack on the ester bond. The tetrahedral transition state is stabilised by an oxyanion hole formed by the amide of Gly166 and 2 water molecules. His162 protonates the leaving group and then deprotonates a water molecule to allow its nucleophilic attack on the acylenzyme intermediate. The essential Ca2+ ion increases the nucleophilicity of the serine and polarises the ester carbonyl bond to facilitate the nucleophilic attack. It is also involved in the oxyanion stabilisation.
    Catalytic Residues
    AA Uniprot Uniprot Resid PDB PDB Resid
    Ser P0A921 164 1qd6 115
    His P0A921 162 1qd6 113
    Ser P0A921 172 1qd6 123
    Asn P0A921 176 1qd6 127
    Gly P0A921 166 1qd6 117
    Ser P0A921 126 1qd6 77
    Arg P0A921 167 1qd6 118
    Step Components

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

    Step 1.

    His162 acts as a general base activating the Ser164 hydroxyl group for nucleophilic attack on the carbonyl carbon of the ester bond. The third component of this catalytic triad- Asn176 acts to increase the basicity of the histidine. The oxyanion intermediate formed is stabilized by the amide group of Gly166, the calcium ion and the water molecules coordinated to the calcium.

    Step 2.

    The tetrahedral intermediate collapses and 2-acyl-sn-glycero-3-phosphocholine is eliminated.

    Step 3.

    His162 activates water for nucleophilic attack and another oxyanion intermediate is formed.

    Step 4.

    The tetrahedral intermediate collapses and Ser164 is eliminated.


    The products of the reaction.

Reaction Parameters

There are no kinetic parameters information for this Enzyme

Associated Proteins

Protein name Organism
Phospholipase A1 1 Lesser banded hornet
Phospholipase A1 2 Lesser banded hornet
Phospholipase A1 verutoxin-2b Asian yellow-legged hornet
Phospholipase A1 VesT1.02 Greater banded hornet
Phospholipase A1 4 European paper wasp