UMMS Affiliation

Department of Medicine

Publication Date


Document Type



Amino Acid Sequence; Amino Acids; Animals; Binding Sites; Catalysis; Computational Biology; Cysteine; Histidine Decarboxylase; Molecular Sequence Data; Mutagenesis, Site-Directed; Rats; Sequence Homology, Amino Acid; Swine; Trypsin; Tyrosine


Computational Biology | Genetics and Genomics | Molecular Genetics


HDC (L-histidine decarboxylase), the enzyme responsible for the catalytic production of histamine from L-histidine, belongs to an evolutionarily conserved family of vitamin B6-dependent enzymes known as the group II decarboxylases. Yet despite the obvious importance of histamine, mammalian HDC enzymes remain poorly characterized at both the biochemical and structural levels. By comparison with the recently described crystal structure of the homologous enzyme L-DOPA decarboxylase, we have been able to identify a number of conserved domains and motifs that are important also for HDC catalysis. This includes residues that were proposed to mediate events within the active site, and HDC proteins carrying mutations in these residues were inactive when expressed in reticulocyte cell lysates reactions. Our studies also suggest that a significant change in quartenary structure occurs during catalysis. This involves a protease sensitive loop, and incubating recombinant HDC with an L-histidine substrate analogue altered enzyme structure so that the loop was no longer exposed for tryptic proteolysis. In total, 27 mutant proteins were used to test the proposed importance of 34 different amino acid residues. This is the most extensive mutagenesis study yet to identify catalytically important residues in a mammalian HDC protein sequence and it provides a number of novel insights into the mechanism of histamine biosynthesis.

DOI of Published Version



Biochem J. 2004 Apr 15;379(Pt 2):253-61. Link to article on publisher's site

Journal/Book/Conference Title

The Biochemical journal

Related Resources

Link to article in PubMed

PubMed ID




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