Reaction Properties of the Ascorbic Acid Oxidase from Myrothecium verrucaria1
AUTOR(ES)
Lillehoj, E. B.
RESUMO
Ascorbic acid oxidase activity in Myrothecium verrucaria extracts resulted in O2 uptake exceeding 0.5 mole per mole of ascorbic acid and in CO2 evolution. Measurement of oxidized ascorbic acid at completion of the reaction demonstrated that an average of 10% of the oxidized product disappeared. A comparison of the gas exchange data with the amount of ascorbic acid not accounted for indicated that the reaction could not be explained by independent oxidase and oxygenase systems. Chromatographic examination of the reaction mixtures identified l-threonic acid. Experiments with ascorbic acid-1-14C showed that C-1 was partially decarboxylated during the oxidation. Test of the fungal extracts for enzymes that might explain the deviation from expected stoichiometry showed that phenolase, glutathione reductase, cytochrome oxidase, peroxidase and oxalic decarboxylase were not involved. Addition of azide in concentrations sufficient to block catalase increased excess O2 consumption about 65%. No enzymes were found that could directly attack oxidized ascorbic acid. H2O2 accumulated during oxidation in azide-blocked systems.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=550575Documentos Relacionados
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