PROSITE documentation PDOC00443

Alpha-galactosidase signature


α-galactosidase (EC (melibiase) [1] catalyzes the hydrolysis of melibiose into galactose and glucose. In man, the deficiency of this enzyme is the cause of Fabry's disease (X-linked sphingolipidosis). α-galactosidase is present in a variety of organisms. There is a considerable degree of similarity in the sequence of α-galactosidase from various eukaryotic species.

Escherichia coli α-galactosidase (gene melA), which requires NAD and magnesium as cofactors, is not structurally related to the eukaryotic enzymes; by contrast, an Escherichia coli plasmid encoded α-galactosidase (gene rafA) [2] contains a region of about 50 amino acids which is similar to a domain of the eukaryotic α-galactosidases.

α-N-acetylgalactosaminidase (EC [3] catalyzes the hydrolysis of terminal non-reducing N-acetyl-D-galactosamine residues in N-acetyl-α-D-galactosaminides. In man, the deficiency of this enzyme is the cause of Schindler and Kanzaki diseases. The sequence of this enzyme is highly related to that of the eukaryotic α-galactosidases.

We selected, as a signature pattern for these enzymes, the N-terminal part of the conserved domain. The pattern contains two conserved aspartic acid residues which could be involved in the catalytic mechanism.


These proteins belong to families 27 and 36 in the classification of glycosyl hydrolases [4,E1].

Expert(s) to contact by email:

Henrissat B.

Last update:

December 2004 / Pattern and text revised.

Technical section

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

ALPHA_GALACTOSIDASE, PS00512; Alpha-galactosidase signature  (PATTERN)


1AuthorsDey P.M., Pridham J.B.C.
TitleBiochemistry of -galactosidases.
SourceAdv. Enzymol. 36:91-130(1972).
PubMed ID4561015

2AuthorsAslanidis C., Schmid K., Schmitt R.
TitleNucleotide sequences and operon structure of plasmid-borne genes mediating uptake and utilization of raffinose in Escherichia coli.
SourceJ. Bacteriol. 171:6753-6763(1989).
PubMed ID2556373

3AuthorsWang A.M., Bishop D.F., Desnick R.J.
TitleHuman alpha-N-acetylgalactosaminidase-molecular cloning, nucleotide sequence, and expression of a full-length cDNA. Homology with human alpha-galactosidase A suggests evolution from a common ancestral gene.
SourceJ. Biol. Chem. 265:21859-21866(1990).
PubMed ID2174888

4AuthorsHenrissat B.
TitleA classification of glycosyl hydrolases based on amino acid sequence similarities.
SourceBiochem. J. 280:309-316(1991).
PubMed ID1747104


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