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. © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
Thompson, J., Pikis, A., Rich, J., Hall, B. G., & Withers, S. G. (2013). α-Galacturonidase(s): A new class of Family 4 glycoside hydrolases with strict specificity and a unique CHEV active site motif. FEBS Letters, 587(6), 799–803. https://doi.org/10.1016/j.febslet.2013.02.004