Isochorismate pyruvate lyase (IPL, EC 4.2.99.21) is an enzyme responsible for catalyzing part of the pathway involved in the formation of salicylic acid.

It catalyzes the elimination of the enolpyruvyl side chain from isochorismate to make salicylate, a precursor to the siderophore pyochelin.

[2] Believed to be a pericyclic reaction, the enzyme's transition state, when transferring a hydrogen from C2 to C9,[3] is cyclic.

[5] In that loop is a positively charged lysine at residue 42, which acts as a lid for this active site.

It is the positive charge on lysine 42, combined with the organization of the substrate once it enters the active site, that allows for the enzyme's transition state stabilization.

Its functions vary depending on the species, but generally salicylate can be used in many bacteria as a building block for various siderophores (organic Fe3+ chelators).