LOCALIZATION OF ENZYMES IN NERVES I. SUCCINIC DEHYDROGENASE AND VITAMIN B

Abstract

Choline esterase is highly concentrated at or near the neuronal surface. This was shown in expts. on the giant fiber of the squid where practically the whole enzyme activity occurred in the sheath, only a negligible amt. of enzyme being present in the axoplasm. Studies were initiated to find out how specific this distribution of choline esterase is, compared with other enzymes, possibly important for nerve activity. Succinic dehydrogenase, widely believed to be essential in respiratory enzyme systems, was detd. in sheath and axoplasm of the giant fiber of the squid. In contrast to the distribution of choline esterase about 90% of the enzyme was localized in the axoplasm. Vit. B1 detd. in its active form, diphosphothiamin, was concentrated at or near the surface many times as high as in the axoplasm. A considerable amt., however, was present in the axoplasm. The cone, at the surface is significant as the acetylation of choline probably requires vit. B1.