PROSITE documentation PDOC00424 [for PROSITE entry PS00488]

Phenylalanine and histidine ammonia-lyases active site


Phenylalanine ammonia-lyase (EC (PAL) is 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.

Histidine ammonia-lyase (EC (histidase) catalyzes the first step in histidine degradation, the removal of an ammonia group from histidine to produce urocanic acid.

The two types of enzymes are functionally and structurally related [1]. They are the only enzymes which are known to have the modified amino acid dehydro-alanine (DHA) in their active site. A serine residue has been shown [2,3,4] 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.

Last update:

April 2006 / Pattern revised.

Technical section

PROSITE method (with tools and information) covered by this documentation:

PAL_HISTIDASE, PS00488; Phenylalanine and histidine ammonia-lyases signature  (PATTERN)


1AuthorsTaylor R.G., Lambert M.A., Sexsmith E., Sadler S.J., Ray P.N., Mahuran D.J., McInnes R.R.
TitleCloning and expression of rat histidase. Homology to two bacterial histidases and four phenylalanine ammonia-lyases.
SourceJ. Biol. Chem. 265:18192-18199(1990).
PubMed ID2120224

2AuthorsLanger M., Reck G., Reed J., Retey J.
TitleIdentification of serine-143 as the most likely precursor of dehydroalanine in the active site of histidine ammonia-lyase. A study of the overexpressed enzyme by site-directed mutagenesis.
SourceBiochemistry 33:6462-6467(1994).
PubMed ID8204579

3AuthorsSchuster B., Retey J.
TitleSerine-202 is the putative precursor of the active site dehydroalanine of phenylalanine ammonia lyase. Site-directed mutagenesis studies on the enzyme from parsley (Petroselinum crispum L.).
SourceFEBS Lett. 349:252-254(1994).
PubMed ID8050576

4AuthorsTaylor R.G., McInnes R.R.
TitleSite-directed mutagenesis of conserved serines in rat histidase. Identification of serine 254 as an essential active site residue.
SourceJ. Biol. Chem. 269:27473-27477(1994).
PubMed ID7961661

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