Subcellular localization of diamine oxidase in rabbit kidney cortex.

The intracellular localization of diamine oxidase (EC 1.4.3.6) in rabbit kidney cortex was studied. The distribution of diamine oxidase in the subcellular fractions, obtained by modifying the classical method of Wattiaux-De Coninck, S., Rutgeerts, M.T. and Wattiaux, R. (Biochim. Biophys. Acta (1965) 105, 446-459) demonstrated that this activity is concentrated (greater than 60%) in the microsomal fraction. Biochemical and morphological data indicate a 20-30% contamination of this fraction by plasma membrane and brush border fragments. Subfractionation of the microsomes, obtained by centrifuging in a continuous sucrose-Ficoll gradient (d 1.038-1.064) for 75 min, showed that diamine oxidase is concentrated in membrane deriving from the endoplasmic reticulum. In fact the bulk of diamine oxidase activity was recovered in a subfraction of the gradient which was shown both biochemically and morphologically to derive from the endoplasmic reticulum. The possible significance of this result is discussed.