title: Interactions of nitrite with catalase: Enzyme activity and reaction kinetics studies.
abstract: Catalase, a heme enzyme, which catalyzes decomposition of hydrogen peroxide to water and molecular oxygen, is one of the main enzymes of the antioxidant defense system of the cell. Nitrite, used as a food preservative has long been regarded as a harmful compound due to its ability to form carcinogenic nitrosamines. Recently, much evidence has been presented that nitrite plays a protective role as a nitric oxide donor under hypoxic conditions. In this work the effect of nitrite on the catalytic reactions of catalase was studied. Catalase was inhibited by nitrite, and this process was pH-dependent. IC50values varied from about 1μM at pH5.0 to about 150μM of nitrite at pH7.4. The presence of chloride significantly enhanced nitrite-induced catalase inhibition, in agreement with earlier observations. The kinetics of the reactions of nitrite with ferric catalase, its redox intermediate, Compound I, and catalase inactive form, Compound II, was also studied. Possible mechanisms of nitrite-induced catalase inhibition are analyzed and the biological consequences of the reactions of catalase with nitrite are discussed.
authors.affiliation: Faculty of Chemistry, Institute of Applied Radiation Chemistry, Lodz University of Technology (TUL), Wroblewskiego 15, 93-590 Lodz, Poland.
authors.forename: Justyna
authors.initials: J
authors.lastname: Krych-Madej
authors.affiliation: Faculty of Chemistry, Institute of Applied Radiation Chemistry, Lodz University of Technology (TUL), Wroblewskiego 15, 93-590 Lodz, Poland. Electronic address: lgebicka@mitr.p.lodz.pl.
authors.forename: Lidia
authors.initials: L
authors.lastname: Gebicka
mesh_terms: D002374:Catalase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D006861:Hydrogen Peroxide; D006863:Hydrogen-Ion Concentration; D020128:Inhibitory Concentration 50; D007700:Kinetics; D009573:Nitrites / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D010084:Oxidation-Reduction
chemical_list: D009573:Nitrites; D006861:Hydrogen Peroxide; D002374:Catalase
keywords: Catalase; Enzyme inhibition; Nitrite