Oxygen transferases

Bleomycins are thought to react with DNA and cause strand scission they have also been shown to have a type of oxygen transferase activity.1... 

In this review I propose to develop the idea that molecular (dissolved) oxygen is metabolized by three types of enzymes, which I tvill call oxygen transferases, mixed function oxidases, and electron transfer oxidases. 

Tracer studies of the fate of oxygen consumed during protocate-chuic acid cleavage have not been carried ocit, but because of oxygen stoichiometry, dependence of the enzyme upon ferrous ions, and resemblance of the over-all reaction to those catalyzed by pyrocate-chase, homogentisate oxidase, and 3-hydroxyanthranilate oxidase (compare 171), it is reasonable to classify protocatechuic acid oxidase as an oxygen transferase. 

In addition to activities ordinarily ascribed to them, peroxidase and catalase possess properties as oxygen transferases and mixed function oxidases. They may exist in functionally active ferrous forms which have, like hemc lobin and myoglobin, the property of combining with molecular oxygen. This oxygen may be transferred to substrate, or be reduced in steps. For purposes of the present review, mechanisms that have been proposed for peroxidatic and catalatic oxidations will be summarized and followed by discussion of dihydroxyfumaric acid oxidase, tryptophan oxidase, and indolyl-acetic oxidase and related oxidases, and indole oxidase. All of these have properties in common with peroxidase and catalase. 

In this review the enzymes that catalyze the reactions of molecular oxygen have been classified in three major groups the oxygen transferases, the mixed function oxidases, and the electron transfer oxidases. With the exception of lipoxidase, the oxygen transferases contain heavy metal which appears to be active in reduced form. In order to explain the experimental observations, particularly those involving tracer oxygen, the transfer of a molecule of oxygen to sub-... 

Oxygen Transferases. The typical reaction of these enzymes is the cleavage of an aromatic ring the product has two C=0 groups at the points left after C=C scission. The mechanism calls for the addition of an oxygen molecule forming, as an intermediate, a cyclic peroxide ... 

All in all, the evidence is consistent with a mechanism of free radical attack followed by addition of molecular oxygen directly via either an oxygen transferase, a mixed function oxidase (Mason, 1957), or a peroxidase. The most prevalent site of the bacterial attack is a terminal carbon atom of the n-alkanes, and in the liquid alkanes (> Cg) this is the only known locus. However, the formation from the gaseous alkanes of homologous products oxygenated in the 2-position along with products oxidized in the terminal carbon atom is indicative of a different situation in the short-chain hydrocarbons. Here either two independent mechanisms exist for the bacterial oxidation, i.e., attack at the terminal carbon and attack at the 2-carbon, or both are manifestations of a common mechanism. Multiple sites of free radical attack are typical of chemical oxidation of alkanes, and an equilibrium mechanism explaining this has been invoked (Leadbetter and Foster, 1960) to account for the bacterial results (Fig. 2). 

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