THE ASSOCIATION OF MANNITOL OXIDASE WITH A DISTINCT ORGANELLE IN THE DIGESTIVE GLAND OF THE TERRESTRIAL SLUG ARION-ATER

Post nuclear supernatants prepared from homogenates of the digestive g land of the slug Arion ater were analysed by rate-dependent and densit y-dependent density gradient zonal centrifugation. Mannitol oxidase ca rrying structures exhibited distinct centrifugal behaviour sedimenting more slowly than mitochondria, lysosomes and peroxisomes but faster t han microsomes, and banding sharply at a density of 1.15 g/ml in sucro se gradients. By combining rate and isopycnic centrifugations mannitol oxidase carrying structures were largely separated from contaminating organelles. Electron microscopic examination of such mannitol oxidase -enriched fractions revealed the predominant presence of distinct stru ctures of tubular form. SDS PAGE analysis indicated that the major pol ypeptide present had a mass of approximately 68 kDa corresponding to t he major subunit previously reported for partially purified mannitol o xidase of Helix aspersa.