Metallo-oxidases

Some Internal Metallo-Oxidases in Aerobic Prokaryotes... 

Laccase is perhaps the metallo-enzyme most widely used for this aim. Laccases are a family of multicopper ( blue copper ) oxidases widely distributed in nature Many laccases have fungal origin, while others are produced in plants. They contain four Cu(II) ions, and catalyse the one-electron oxidation of four molecules of a reducing substrate with the concomitant four-electron reduction of oxygen to water . In view of their low redox potential, which is in the range of 0.5-0.8 V vs. NHE depending on the fungal source laccases typically oxidize phenols (phenoloxidase activity) or anilines. 

Polyphenol oxidase (PPO) (EC 1.14.18.1 monophenol monooxygenase [tyrosinase] or EC 1.10.3.2 0-diphenol 02-oxidoreductase) is one of the more important enzymes involved in the formation of black tea polyphenols. The enzyme is a metallo-protein thought to contain a binudear copper active site. The substance PPO is an oligomeric particulate protein thought to be bound to the plant membranes. The bound form of the enzyme is latent and activation is likely to be dependent upon solubilization of the protein (35). PPO is distributed throughout the plant (35) and is localized within in the mitochondria (36), the cholorplasts (37), and the peroxisomes (38). Using antibody techniques, polyphenol oxidase activity has also been localized in the epidermis palisade cells (39). Reviews on the subject of PPO are available (40—42). 

Catalases and peroxidases. Many iron and copper proteins do not bind 02 reversibly but "activate" it for further reaction. We will look at such metallo-protein oxidases in Chapter 18. Here we will consider heme enzymes that react not with 02 but with peroxides. The peroxidases,1943 which occur in plants, animals, and fungi, catalyze the following reactions (Eq. 16-6,16-7) ... 

The most detailed spectroscopic and electronic structure studies of metallo-mono(dithiolenes) have focused on the nature of ligand-to-ligand charge transfer (LLCT) excitations in [M(diimine)(dithiolene)] complexes (112, 250-257, 262, 264, 295-301) and in monooxo molybdenum dithiolenes (19, 20, 22, 23) as models for pyranopterin molybdenum enzymes such as sulfite oxidase (SO). Since metallo-mono(dithiolenes) generally possess little or no symmetry, detailed spectrosopic and electronic structure studies of this class of metallo-dithiolenes have only recently begun to appear. The analysis of the spectroscopic data has been aided by the fact that the dithiolene-to-metal charge... 

Knowles, P. F., Lowe, D. J., Peters, J., Thomeley, R. N. F., and Yadav, K. D. S., 1983, Kinetic and magnetic resonance studies on amine oxidases, in iThe Coordination Chemistry of Metallo-Enzymesi Edited by Bertini, I., Drago, R. S., and Luchinat, C. Reidel publishers, 159nl76. 

BACTERIAL OXIDASES, COPPER RESISTANCE, AND METALLO-OXIDATION... 

Copper Proteins Oxidases Copper Proteins with Dinnclear Active Sites Copper Proteins with Type 1 Sites Metallo-chaperones Metal Ion Homeostasis. 

Lipoxygenase Malate dehydrogenase Metallo-endopeptidase N-Methyl transferase Monoamine oxidase Mixed-function oxidase (cytochrome P450 dependent) NADH2 diaphorase NADPH2 diaphorase Neutral endopeptidase 24.11 Nitro oxide synthase Nitro reductase 5 -Nucleotidase Peroxidase... 

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