Bernard Henrissat's paper presents a classification of glycosyl hydrolases based on amino acid sequence similarities. The study compared the amino acid sequences of 301 glycosyl hydrolases and related enzymes, classifying 291 sequences into 35 families. Only 10 sequences could not be assigned to any family. The classification revealed that 18 families are monospecific, while 17 are polyspecific. The implications of this classification on the folding characteristics, mechanism of action, and evolution of carbohydrate metabolism are discussed. The paper suggests that the enzyme classification system should be revised to better reflect sequence and structural similarities, especially with the increasing availability of sequence and structural data. The classification is based on significant amino acid similarity and is expected to be useful for homology modeling and enzyme crystallization. The findings also highlight the importance of studying the evolution of glycosyl hydrolases to trace the evolution of carbohydrates.Bernard Henrissat's paper presents a classification of glycosyl hydrolases based on amino acid sequence similarities. The study compared the amino acid sequences of 301 glycosyl hydrolases and related enzymes, classifying 291 sequences into 35 families. Only 10 sequences could not be assigned to any family. The classification revealed that 18 families are monospecific, while 17 are polyspecific. The implications of this classification on the folding characteristics, mechanism of action, and evolution of carbohydrate metabolism are discussed. The paper suggests that the enzyme classification system should be revised to better reflect sequence and structural similarities, especially with the increasing availability of sequence and structural data. The classification is based on significant amino acid similarity and is expected to be useful for homology modeling and enzyme crystallization. The findings also highlight the importance of studying the evolution of glycosyl hydrolases to trace the evolution of carbohydrates.