α-Galacturonidase(s): A new class of Family 4 glycoside hydrolases with strict specificity and a unique CHEV active site motif

► Family 4 glycosidases with a CHEV active site motif form a monophyletic clade. ► The crystal structure of one CHEV glycosidase (LplD) was determined in 2008. ► The catalytic activity of these enzymes has until now remained unknown. ► These enzymes are α-galacturonidases. ► They employ a non-canonical redox-assisted catalytic mechanism.