Distribution of three enzymes of gamma-aminobutyric acid metabolism in monkey retina.

The distributions of glutamate decarboxylase (EC 4.1.1.15), gamma-aminobutyric acid transaminase (EC 2.6.1.19), and succinate semialdehyde dehydrogenase (EC 1.2.1.24) were determined in monkey retina. The decarboxylase was almost restricted to the inner plexiform layer. The transaminase was also highest in this layer, but activities were 40% as high in the adjacent third of the inner nuclear layer and in the ganglion cell and fiber layers. Succinate semialdehyde dehydrogenase was distributed very differently. Although it also showed a peak of activity in the inner plexiform layer, there was a second equal peak in the photoreceptor inner segment layer and a smaller peak in the outer plexiform layer, regions where both gamma-aminobutyric acid transaminase and glutamate decarboxylase were essentially absent.