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NnaC (CMP-NeuNAc synthetase) _like subfamily of SGNH_hydrolases, a diverse family of lipases and esterases. The tertiary fold of the enzyme is substantially different from that of the alpha/beta hydrolase family and unique among all known hydrolases; its active site closely resembles two of the three components of typical Ser-His-Asp(Glu) triad from other serine hydrolases. E. coli NnaC appears to be involved in polysaccharide synthesis.