Biomaterial Database

Manganese(II) oxidation by manganese peroxidase from the basidiomycete Phanerochaete chrysosporium. Kinetic mechanism and role of chelators. 1992

H Wariishi, and K Valli, and M H Gold

Department of Chemical and Biological Sciences, Oregon Graduate Institute of Science and Technology, Beaverton 97006-1999.

Manganese oxidation by manganese peroxidase (MnP) was investigated. Stoichiometric, kinetic, and MnII binding studies demonstrated that MnP has a single manganese binding site near the heme, and two MnIII equivalents are formed at the expense of one H2O2 equivalent. Since each catalytic cycle step is irreversible, the data fit a peroxidase ping-pong mechanism rather than an ordered bi-bi ping-pong mechanism. MnIII-organic acid complexes oxidize terminal phenolic substrates in a second-order reaction. MnIII-lactate and -tartrate also react slowly with H2O2, with third-order kinetics. The latter slow reaction does not interfere with the rapid MnP oxidation of phenols. Oxalate and malonate are the only organic acid chelators secreted by the fungus in significant amounts. No relationship between stimulation of enzyme activity and chelator size was found, suggesting that the substrate is free MnII rather than a MnII-chelator complex. The enzyme competes with chelators for free MnII. Optimal chelators, such as malonate, facilitate MnIII dissociation from the enzyme, stabilize MnIII in aqueous solution, and have a relatively low MnII binding constant.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D007773	Lactates	Salts or esters of LACTIC ACID containing the general formula CH3CHOHCOOR.
D008314	Malonates	Derivatives of malonic acid (the structural formula CH2(COOH)2), including its salts and esters.
D008345	Manganese	A trace element with atomic symbol Mn, atomic number 25, and atomic weight 54.94. It is concentrated in cell mitochondria, mostly in the pituitary gland, liver, pancreas, kidney, and bone, influences the synthesis of mucopolysaccharides, stimulates hepatic synthesis of cholesterol and fatty acids, and is a cofactor in many enzymes, including arginase and alkaline phosphatase in the liver. (From AMA Drug Evaluations Annual 1992, p2035)
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D010544	Peroxidases		Ovoperoxidase
D002264	Carboxylic Acids	Organic compounds containing the carboxy group (-COOH). This group of compounds includes amino acids and fatty acids. Carboxylic acids can be saturated, unsaturated, or aromatic.	Carboxylic Acid,Acid, Carboxylic,Acids, Carboxylic
D002614	Chelating Agents	Chemicals that bind to and remove ions from solutions. Many chelating agents function through the formation of COORDINATION COMPLEXES with METALS.	Chelating Agent,Chelator,Complexons,Metal Antagonists,Chelators,Metal Chelating Agents,Agent, Chelating,Agents, Chelating,Agents, Metal Chelating,Antagonists, Metal,Chelating Agents, Metal
D006861	Hydrogen Peroxide	A strong oxidizing agent used in aqueous solution as a ripening agent, bleach, and topical anti-infective. It is relatively unstable and solutions deteriorate over time unless stabilized by the addition of acetanilide or similar organic materials.	Hydrogen Peroxide (H2O2),Hydroperoxide,Oxydol,Perhydrol,Superoxol,Peroxide, Hydrogen