Bernard Henriissat classified 301 glycosyl hydrolase sequences into 35 families based on amino acid similarities. Of these, 291 sequences could be assigned to 35 families, while 10 sequences could not be classified. The classification revealed 18 monospecific families (each containing only one EC number) and 17 polyspecific families (each containing at least two EC numbers). The study suggests that the current enzyme classification system may need revision due to the increasing availability of sequence and structural data. The classification is based on sequence similarity rather than substrate specificity, which may better reflect the structural and functional relationships among enzymes. The study also discusses the implications of this classification for understanding enzyme folding, mechanism, and the evolution of carbohydrate metabolism. The classification could help in predicting enzyme function and in choosing enzymes for structural studies. The findings suggest that some families may be polyspecific even if they are currently monospecific, and that the classification may be expanded in the future. The study also highlights the importance of structural data in understanding enzyme function and evolution. The classification may serve as a useful tool for studying the evolution of enzyme specificity and carbohydrate metabolism. The study also discusses the molecular mechanism of glycosyl hydrolases, which are thought to act via a general acid catalysis mechanism. The study also discusses the evolutionary aspects of glycosyl hydrolases, including the acquisition of new specificities and the divergence of enzymes to adapt to new substrates. The study suggests that gene duplication may be a way to cope with such evolutionary events. The study also discusses the origins of human LPH and the evolutionary relationships between different glycosyl hydrolases. The study concludes that understanding the evolution of enzymes involved in carbohydrate metabolism can help trace the evolution of carbohydrates themselves.Bernard Henriissat classified 301 glycosyl hydrolase sequences into 35 families based on amino acid similarities. Of these, 291 sequences could be assigned to 35 families, while 10 sequences could not be classified. The classification revealed 18 monospecific families (each containing only one EC number) and 17 polyspecific families (each containing at least two EC numbers). The study suggests that the current enzyme classification system may need revision due to the increasing availability of sequence and structural data. The classification is based on sequence similarity rather than substrate specificity, which may better reflect the structural and functional relationships among enzymes. The study also discusses the implications of this classification for understanding enzyme folding, mechanism, and the evolution of carbohydrate metabolism. The classification could help in predicting enzyme function and in choosing enzymes for structural studies. The findings suggest that some families may be polyspecific even if they are currently monospecific, and that the classification may be expanded in the future. The study also highlights the importance of structural data in understanding enzyme function and evolution. The classification may serve as a useful tool for studying the evolution of enzyme specificity and carbohydrate metabolism. The study also discusses the molecular mechanism of glycosyl hydrolases, which are thought to act via a general acid catalysis mechanism. The study also discusses the evolutionary aspects of glycosyl hydrolases, including the acquisition of new specificities and the divergence of enzymes to adapt to new substrates. The study suggests that gene duplication may be a way to cope with such evolutionary events. The study also discusses the origins of human LPH and the evolutionary relationships between different glycosyl hydrolases. The study concludes that understanding the evolution of enzymes involved in carbohydrate metabolism can help trace the evolution of carbohydrates themselves.