D-Aspartate oxidase and D-amino acid oxidase are localised in the peroxisomes of terrestrial gastropods

D-Aspartate oxidase and D-amino acid oxidase were found in high activity in the tissues of representative species of terrestrial gastropods. Analytica l subcellular fractionation demonstrated that both of these oxidases co-loc alised with the peroxisome markers, acyl-CoA oxidase and catalase, in the d igestive gland homogenate. Electron microscopy of peak peroxisome fractions showed particles of uniform size with generally well preserved variably el ectron-dense matrices bounded by an apparently single limiting membrane. Ma ny of the particles exhibited a core region of enhanced electron density. C atalase cytochemistry of peak fractions confirmed the peroxisome identity o f the organelles. Peroxisome-enriched subcellular fractions were used to investigate the prop erties of gastropod D-aspartate oxidase and D-amino acid oxidase activities . The substrate and inhibitor specificities of the two activities demonstra ted that two distinct enzymes were present analogous to, but not identical to, the equivalent mammalian peroxisomal enzymes.