Mitochondrial Arginase Activity from Cotyledons of Developing and Germinating Seeds of Vicia faba L.

Differential and sucrose density gradient centrifugation established that about 80% of the total arginase activity (EC 3.5.3.1) in cotyledons of germinating broad bean seeds (Vicia faba L.) was present in the mitochondrial fraction. The mitochondrial arginase activity was enhanced considerably by exposure to osmotic shock, by freezing and thawing, or by Triton X-100 treatment. About 10% of the total arginase activity was recovered from the 40,000g supernatant fraction. During seed maturation, arginase activity in the cotyledons decreased to about one-third of its maximal activity, while increasing over 10-fold during subsequent germination. The time courses of mitochondrial arginase, succinate oxidase, and succinate dehydrogenase activities differed considerably during germination.