title: α-Galacturonidase(s): a new class of Family 4 glycoside hydrolases with strict specificity and a unique CHEV active site motif.
abstract: The catalytic activity of the Family 4 glycosidase LplD protein, whose active site motif is CHEV, is unknown despite its crystal structure having been determined in 2008. Here we identify that activity as being an α-galacturonidase whose natural substrate is probably α-1,4-di-galacturonate (GalUA2). Phylogenetic analysis shows that LplD belongs to a monophyletic clade of CHEV Family 4 enzymes, of which four other members are also shown to be galacturonidases. Family GH 4 enzymes catalyze the cleavage of the glycosidic bond, via a non-canonical redox-assisted mechanism that contrasts with Koshland's double-displacement mechanism.
authors: Microbial Biochemistry and Genetics Section, Laboratory of Cell and Developmental Biology, NIDCR, National Institutes of Health, Bethesda, MD 20892, USA. jthompson@dir.nidcr.nih.gov
authors: John
authors: J
authors: Thompson
authors: Andreas
authors: A
authors: Pikis
authors: Jamie
authors: J
authors: Rich
authors: Barry G
authors: BG
authors: Hall
authors: Stephen G
authors: SG
authors: Withers
mesh_terms: D020816:Amino Acid Motifs; D001412:Bacillus subtilis / Q000737:chemistry / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055162:Biocatalysis; D020134:Catalytic Domain; D004926:Escherichia coli / Q000235:genetics; D005690:Galactose / Q000031:analogs & derivatives* / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D006026:Glycoside Hydrolases; D005690:Galactose