O-GlcNAc processing enzymes: catalytic mechanisms, substrate specificity, and enzyme regulation

► O-GlcNAc levels in cells respond to availability of nutrients including glucose. ► OGT and OGA are the two enzymes processing hundreds of O-GlcNAc modified proteins. ► Catalysis by OGA and OGT is being studied using kinetic and structural approaches. ► OGA processes metabolic derivatives of O-GlcNAc from proteins. ► The substrate specificity and regulation of OGA and OGT merit further attention.