Glycoside hydrolases: catalytic base/nucleophile diversity

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Classical glycoside hydrolase mechanisms rely on a catalytic base/nucleophile.
• Some glycoside hydrolase families deviate from these established catalytic pathways.

Purpose of the Study:

• To explore alternative catalytic mechanisms in glycoside hydrolase families lacking a typical catalytic base/nucleophile.
• To investigate the functional consequences of altering catalytic residues on enzyme specificity.

Main Methods:

• Analysis of diverse glycoside hydrolase families.
• Site-directed mutagenesis to remove catalytic base/nucleophile residues.
• Enzyme activity and substrate specificity assays.

Main Results:

• Identified alternative catalytic strategies, including substrate-assisted catalysis, residue networks, and utilization of non-carboxylate residues or exogenous nucleophiles.
• Demonstrated that mutations removing the catalytic base/nucleophile significantly alter substrate specificity.
• Observed the emergence of novel enzyme functions in modified glycoside hydrolases.

Conclusions:

• Glycoside hydrolase catalysis is more diverse than previously understood.
• The absence of a canonical catalytic base/nucleophile drives the evolution of new enzymatic functions.
• Enzyme engineering by altering catalytic residues offers a route to novel biocatalysts.