Oxidases and oxygenases

Solomon El, Sundaram UM, Machonkin TE. 1996. Multicopper oxidases and oxygenases. Chem Rev 96 2563-2605. 

Flavins are very versatile redox coenzymes. Flavopro-teins are dehydrogenases, oxidases, and oxygenases that catalyze a variety of reactions on an equal variety of substrate types. Since these classes of enzymes do not consist exclusively of flavoproteins, it is difficult to define catalytic specificity for flavins. Biological electron acceptors and donors in flavin-mediated reactions can be two-electron acceptors, such as NAD+ or NADP+, or a variety of one-electron acceptor systems, such as cytochromes (Fe2+/ Fe3+) and quinones, and molecular oxygen is an electron acceptor for flavoprotein oxidases as well as the source of oxygen for oxygenases. The only obviously common aspect of flavin-dependent reactions is that all are redox reactions. 

See also Oxidases and Oxygenases, Reactive Oxygen, Heme, Second Messenger Systems... 

Integrity of Mitochondrial Membranes Uncoupling ETS and Oxidative Phosphorylation Respiratory Control Oxidases and Oxygenases... 

See also The C4 Cycle, Reactive Oxygen (from Chapter 15), Oxidases and Oxygenases (from Chapter 15)... 

Oxygen as a Substrate for Other Metabolic Reactions Oxidases and Oxygenases (Reachon 4)... 

Fig. 19.12. Oxidases and oxygenases. The fate of O2 is shown in blue. S represents an organic substrate.

Several of functional Fe(III)- and Co(II)-phthalocyanines and their polymers as models for catalase, peroxidase, oxidase and oxygenase enzymes were synthesized ([265] and references cited therein). Copolyesters 62 containing Fe(III)- and Cu(II) phthalocyanines were obtained by polycondensation of phthalocyanine dicarboxylic acid dichlorides with terephthalic acid dichloride and aliphatic diols. Green or blue colored fibres could be obtained by melt spinning of the copolyesters containing below 1 mol% of the metal complex [265]. The polymers were investigated as catalysts for the thiol oxidation. 

Supercritical CO2 is gaining importance as a reaction medium. The oxidation of substituted phenols by O2 has been studied in supercritical CO2 using [ N,N -bis(3,5-di-/e t-butylsalicylidene)-1,2-cyclohexanediaminato(2- ) -cobalt(II)] as catalyst Both oxidase and oxygenase activities are observed with 2,6-di-terr-butylphenol as substrate at 70 C and 207 bar total pressure, at an 02 phenol catalyst ratio of 1500 20 1, and a methylimidazole to catalyst ratio of 1.28. Total conversion to 2,6-di-terr-butyl-l,4-benzoquinone and 3,5,3 ,5 -tetra-tm-butyl-4,4 -diphenoquinone took place in 21 h. 

The totally synthetic superstmctured cobalt(II) cyclidene complexes (Figure 61) CoA (vaulted), CoB (unbridged) and CoC (lacunar), function as both oxidase and oxygenase models in oxygenation of substituted phenols . 

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