It has been shown [1,2,E1] that the following glycosyl hydrolases can be, on
the basis of sequence similarities, classified into a single family:
β-galactosidases (EC 18.104.22.168) from bacteria such as Escherichia coli
(genes lacZ and ebgA), Clostridium acetobutylicum, Clostridium
thermosulfurogenes, Klebsiella pneumoniae, Lactobacillus delbrueckii, or
Streptococcus thermophilus and from the fungi Kluyveromyces lactis.
β-glucuronidase (EC 22.214.171.124) from Escherichia coli (gene uidA) and from
One of the conserved regions in these enzymes is centered on a conserved
glutamic acid residue which has been shown , in Escherichia coli lacZ, to
be the general acid/base catalyst in the active site of the enzyme. We have
used this region as a signature pattern. As a second signature pattern we
selected a highly conserved region located some sixty residues upstream from
the active site glutamate.
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