The oxidation of manganese by enzyme systems

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Abstract
The oxidation of Mn++ can be brought about by enzyme systems producing H2O2 such as D-amino-acid oxidase, xanthine oxidase and plant amine oxidase systems coupled with peroxidase systems. With high Mn++ concns. the oxidation was demonstrated by the increased O2 uptake and by estimation of the Mn oxidation product with hydrazine. The oxidation product accumulates in both pyrophosphate and orthophosphate media. With low Mn++ concns. the oxidation was demonstrated by the increased O2 uptake of the system in presence of oxalic acid. Under these conditions the Mn is involved in a cycle of oxidation and reduction. The oxidation of Mn++ by peroxidase systems can be used as a test for H2O2. By this test it has been shown that plant alpha-hydroxyacid oxidase produces H2O2 while catalysing the oxidation of L-lactic and glycollic acids.