| SCOP superfamily ID | superfamiily description | corresponding fold description |
|---|---|---|
| d.153.1 | N-terminal nucleophile aminohydrolases (Ntn hydrolases) N-terminal residue provides two catalytic groups, nucleophile and proton donor ! | Ntn hydrolase-like 4 layers: alpha/beta/beta/alpha; has an unusual sheet-to-sheet packing |
| d.153.2 | Archaeal IMP cyclohydrolase PurO has a putative active site in the same topological location as the Ntn hydrolase but lacks the N-terminal nucleophile ! | Ntn hydrolase-like 4 layers: alpha/beta/beta/alpha; has an unusual sheet-to-sheet packing |