SOME PROPERTIES OF GLUTAMATE DECARBOXYLASE AND THE CONTENT OF PYRIDOXAL PHOSPHATE IN BRAINS OF THREE VERTEBRATE SPECIES

Publisher Website
Google Scholar
Abstract
—Some properties of glutamate decarboxylase (GAD) were studied in the brain of the carp (Carassius auratus), the pigeon (Columbia livia) and the mouse (Mus musculus). The optimum pH for GAD in the three species was 6·3‐6·5. In the three species studied, GAD activity of brain homogenates in water was higher than that of homogenates in buffer. The supernatant from homogenates in Triton‐X‐100 gave an enzyme preparation which showed greater activation by pyridoxal phosphate than those obtained from complete water or buffer homogenates or from the supernatant of Water homogenates.In the absence of pyridoxal phosphate, the activity of carp GAD was considerably lower than that of mouse or pigeon GAD. The addition of pyridoxal phosphate resulted in a much greater activation of carp GAD than that of pigeon or mouse GAD. Pyridoxal phosphate content was also measured in brains of the species studied. The difference between coenzyme levels in carp and mouse was very small in comparison to the difference in GAD activity in the absence of exogenous coenzyme. The pyridoxal phosphate content of pigeon brain was higher than that of the other two species.