Hakansson_2002_Int.J.Biol.Macromol_30_273

The active site structures of hydrolytic enzymes representing five different protein folds were compared. They contain a strand-helix motif with an active site nucleophile occupying a less favourable region in the Ramachandran plot, as previously described for the alpha/beta-hydrolases. Comparison of the different structures enabled a characterisation of the common denominator and suggests an explanation for the unusual Ramachandran values. According to this, the Ramachandran values reflect the orientation of one of the backbone amino group that stabilises the oxyanion intermediate of catalysis.