Studies on a thermostable nitrilase from Staphylococcus Sp and its In-silico characterisation

An inducible and heterocyclic thermostable nitrilase was obtained from Staphylococcus sp. KP789135.1. The whole cell nitrilase was active at 50 °C temperature and neutral pH with a half-life of 4 h at 50 °C and 2.5 h at 60 °C. Metal ions such as Fe3+, Mg2+, and Ca2+ enhanced the biocatalytic activity while Ag2+, Hg2+, and Cu2+ completely inhibited biocatalysis, which confirmed the presence of thiol group in the catalytic site. Staphylococcus sp. KP789135.1 has broad hydrolytic activity towards heterocyclic nitriles and few amides. It showed high tolerance against 3-cyanopyridine (5 mM - 20 mM). The calculated Km and Vmax were 1.33 mM and 0.98 U, lower km values demonstrated the highest affinity towards 3-cyanopyridine. In silico study revealed 99% similarity with Staphylococcus strain. The 3D structures were deduced from I-TASSER server and validated from PROCHECK, found relatively low % of amino acid residues has phi/psi angles in the disallowed region that suggest the acceptability of Ramachandran plot in the present work. Docking study revealed 3-cyanopyridine has lowest potential energy (potential energy OPLS -7.00745) and thus showed more stable enzyme ligand interaction. This is the first report on biotransformation of 3-cyanopyridine to nicotinic acid using thermostable nitrilase from Staphylococcus sp.