Properties of syringaldazine oxidase/peroxidase in maize roots.

An easily prepared and reproducible reagent for peroxidase was obtained by dissolving syringaldazine in dimethylsulfoxide (DMSO). H ethanol was a strong inhibitor of maize root peroxidase activity, DMSO, at the concentration required to solubilise the hydrogen donor, was without effect on peroxidase activity and was very suitable for isoperoxidase staining after disc gel electrophoresis. Using this method, seven isoperoxidases were found. Three of these were wall-bound isoperoxidases. The affinity of peroxidases for syringaldazine was much higher than that obtained with other hydrogen donors. The Km for hydrogen peroxide was very low if syringaldazine was used as hydrogen donor. The high level of peroxidase activity in maize root cortex imply that syringaldazine oxidase plays another role than in the polymerisation of lignin precursors.