Radiochemical Assay of Diamine Oxidase

Diamine oxidase activity (E.C. 1.4.3.6) can be measured by a modification of the method first reported by Okuyama and Kobayashi ( 1 ), as developed by Trydingetal. ( 2 – 4 ). Oxidation of [1,4- ¹⁴ C]putrescine by diamine oxidase leads to the formation of γ-[ ¹⁴ C]-aminobutylaldehyde, which rapidly and spontaneously undergoes an internal cyclization to form the internal aldimine ring compound, ΔA ¹ -[ ¹⁴ C]pyrroline (Fig. 1 ). The pyrroline may undergo further spontaneous polymerization ( 5 ). Unlike putrescine, which is very soluble in water, Δ ¹ -pyrroline and its polymers are soluble in toluene at alkaline pH and may be easily separated from the substrate by solvent extraction. This assay system has been extensively reviewed ( 6 – 10 ).

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