Interaction Mechanism between Pseudomonas Species Lipase and Nitro Compounds

Abstract

The object of this work was to determine the enzyme kinetics for Pseudomonas species lipase catalyzed hydrolysis of substrate 4-nitrophenyl butyrate in the presence of nitro compounds such as nitroglycerin, 2,4,6-trinitrotoluene (TNT), picric acid, styphnic acid, hexahydro-1,3,5-trinitrotriazocine (RDX), octahydro-1,3,5,7-tetranitrotriazocine (HMX) and hexanitrohexaazaisowurtzitane (HNIW) in vitro. Kinetically, picric acid and styphnic acid were the mixed-type inhibitors but TNT, RDX and HNIW were the essential activators of the enzyme in the presence of a detergent triton-X 100. Interestingly, HMX and nitroglycerin were neither an inhibitor nor an activator of the enzyme. From chemical structure point of view, hydrophilic nitro compounds such as picric acid and styphnic acid are capable to enter the hydrophilic active site of lipase and become inhibitors of the enzyme, while hydrophobic nitro compounds such as TNT, RDX and HNIW presumably mix with Triton-X-100 and bind to the co-lipase binding site of the enzyme and become the essential activators of the enzyme.