PROSITE documentation PDOC00329
DDC / GAD / HDC / TyrDC pyridoxal-phosphate attachment site


Three different enzymes - all pyridoxal-dependent decarboxylases - seem to share regions of sequence similarity [1,2,3,4], especially in the vicinity of the lysine residue which serves as the attachment site for the pyridoxal-phosphate (PLP) group. These enzymes are:

  • Glutamate decarboxylase (EC (GAD). Catalyzes the decarboxylation of glutamate into the neurotransmitter GABA (4-aminobutanoate).
  • Histidine decarboxylase (EC (HDC). Catalyzes the decarboxylation of histidine to histamine. There are two completely unrelated types of HDC: those that use PLP as a cofactor (found in Gram-negative bacteria and mammals), and those that contain a covalently bound pyruvoyl residue (found in Gram-positive bacteria).
  • Aromatic-L-amino-acid decarboxylase (EC (DDC), also known as L-dopa decarboxylase or tryptophan decarboxylase. DDC catalyzes the decarboxylation of tryptophan to tryptamine. It also acts on 5-hydroxy- tryptophan and dihydroxyphenylalanine (L-dopa).
  • Tyrosine decarboxylase (EC (TyrDC) which converts tyrosine into tyramine, a precursor of isoquinoline alkaloids and various amides.
  • Cysteine sulfinic acid decarboxylase (EC
  • L-2,4-diaminobutyrate decarboxylase (EC 4.1.1.-) (DABA decarboxylase).

These enzymes are collectively known as group II decarboxylases [3,4].

Last update:

April 2006 / Pattern revised.


Technical section

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

DDC_GAD_HDC_YDC, PS00392; DDC / GAD / HDC / TyrDC pyridoxal-phosphate attachment site  (PATTERN)


1AuthorsJackson F.R.
TitleProkaryotic and eukaryotic pyridoxal-dependent decarboxylases are homologous.
SourceJ. Mol. Evol. 31:325-329(1990).
PubMed ID2124279

2AuthorsJoseph D.R. Sullivan P.M. Wang Y.-M. Kozak C. Fenstermacher D.A. Behrendsen M.E. Zahnow C.A.
TitleCharacterization and expression of the complementary DNA encoding rat histidine decarboxylase.
SourceProc. Natl. Acad. Sci. U.S.A. 87:733-737(1990).
PubMed ID2300558

3AuthorsSandmeier E. Hale T.I. Christen P.
TitleMultiple evolutionary origin of pyridoxal-5'-phosphate-dependent amino acid decarboxylases.
SourceEur. J. Biochem. 221:997-1002(1994).
PubMed ID8181483

4AuthorsIshii S. Mizuguchi H. Nishino J. Hayashi H. Kagamiyama H.
TitleFunctionally important residues of aromatic L-amino acid decarboxylase probed by sequence alignment and site-directed mutagenesis.
SourceJ. Biochem. 120:369-376(1996).
PubMed ID8889823

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