tailieunhanh - Báo cáo khoa học: Reduction of aliphatic nitroesters and N-nitramines by Enterobacter cloacae PB2 pentaerythritol tetranitrate reductase

Enterobacter cloacae PB2 NADPH:pentaerythritol tetranitrate reductase (PETNR) performs the biodegradation of explosive organic nitrate esters via their reductive denitration. In order to understand the enzyme substrate specificity, we have examined the reactions of PETNR with organic nitrates (n= 15) and their nitrogen analogues,N-nitramines (n= 4). | ễFEBS Journal Reduction of aliphatic nitroesters and N-nitramines by Enterobacter cloacae PB2 pentaerythritol tetranitrate reductase Quantitative structure-activity relationships 1 1 1 2 Henrikas Nivinskas Jonas Sarlauskas Zilvinas Anusevicius Helen S. Toogood Nigel S. Scrutton2 and Narimantas Cenas1 1 Institute of Biochemistry Vilnius Lithuania 2 Faculty of Life Sciences Manchester Interdisciplinary Biocentre University of Manchester UK Keywords glycerol trinitrate hexahydro-1 3 5-trinitro-1 3 5-triazine mechanism of reduction Old Yellow Enzyme pentaerythritol tetranitrate reductase Correspondence N. Cenas Institute of Biochemistry Mokslininku 12 LT 08662 Vilnius Lithuania Fax 370 5 2729196 Tel 370 5 2729042 E-mail ncenas@ Received 28 July 2008 revised 9 October 2008 accepted 15 October 2008 doi Enterobacter cloacae PB2 NADPH pentaerythritol tetranitrate reductase PETNR performs the biodegradation of explosive organic nitrate esters via their reductive denitration. In order to understand the enzyme substrate specificity we have examined the reactions of PETNR with organic nitrates n 15 and their nitrogen analogues N-nitramines n 4 . The reactions of these compounds with PETNR were accompanied by the release of 1-2 mol of nitrite per mole of compound but were not accompanied by their redox cycling and superoxide formation. The reduction rate constants kcat Km of inositol hexanitrate diglycerol tetranitrate erythritol tetranitrate mannitol hexanitrate and xylitol pentanitrate were similar to those of the established PETNR substrates PETN and glycerol trinitrate whereas the reactivities of hexahydro-1 3 5-trinitro-1 3 5-triazine and octahydro-1 3 5 7-tetranitro-1 3 5 7-tetrazocine were three orders of magnitude lower. The log kcat Km value of the compounds increased with a decrease in the enthalpy of formation of the hydride adducts AHf R-O-N OH O or DHf R1 R2 N-N OH O and with an increase in their lipophilicity octanol water .