Some problems associated with measuring monoamine oxidase activity in the presence of sodium azide

Summary

The colourimetric assay of monoamine oxidase activity, as hydrogen peroxide production, normally requires the use of sodium azide to inhibit breakdown of hydrogen peroxide by catalase. Sodium azide was shown to act as an uncompetitive inhibitor of benzylamine deamination with an inhibitor constant of 1.5 mM. Catalase activity of isolated rat liver mitochondria could be eliminated with the irreversible inhibitor of catalase, 3-amino-l,2,4-triazole. The treatment did not affect benzylamine deaminating activity. The catalase-free preparation could be used to assay monoamine oxidase activity colourimetrically, as hydrogen peroxide production, in the absence of sodium azide.