Functionally and structurally related to phenylalanine ammonia-lyase (EC 4.3.1.5), a key enzyme of plant and fungi phenylpropanoid metabolism which is involved in the biosynthesis of a wide variety of secondary metabolites such as flavanoids, furanocoumarin phytoalexins and cell wall components. These compounds have many important roles in plants during normal growth and in responses to environmental stress. PAL catalyzes the removal of an ammonia group from phenylalanine to form trans-cinnamate.

The two types of enzymes are functionally and structurally related. They are the only enzymes which are known to have the modified amino acid dehydro- alanine in their active site. A serine residue has been shown to be the precursor of this essential electrophilic moiety. The region around this active site residue is well conserved and can be used as a signature pattern.
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