Pseudomonas sp. MCI3434 R-amidase and related proteins (putative class 13 nitrilases)
Pseudomonas sp. MCI3434 R-amidase hydrolyzes (R,S)-piperazine-2-tert-butylcarboxamide to form (R)-piperazine-2-carboxylic acid. It does so with strict R-stereoselectively. Its preferred substrates are carboxamide compounds which have the amino or imino group connected to their beta- or gamma-carbon. This subgroup belongs to a larger nitrilase superfamily comprised of nitrile- or amide-hydrolyzing enzymes and amide-condensing enzymes, which depend on a Glu-Lys-Cys catalytic triad. This superfamily has been classified in the literature based on global and structure based sequence analysis into thirteen different enzyme classes (referred to as 1-13), class 13 represents proteins that at the time were difficult to place in a distinct similarity group. It has been suggested that this subgroup represents a new class. Members of the nitrilase superfamily generally form homomeric complexes, the basic building block of which is a homodimer. Native R-amidase however appears to be a monomer.