The Carbohydrate-Active Enzymes database (CAZy) provides a continuously updated list of the glycoside hydrolase families. Because the fold of proteins is better conserved than their sequences, some of the families can be grouped in ’clans’ :
(i) when new sequences are found to be related to more than one family,
(ii) when the sensitivity of sequence comparison methods is increased or
(iii) when structural determinations demonstrate the resemblance between members of different familiesses