Activity changes of chicken enzymes involved in glutamate and 2-oxoglutarate metabolism at the time of hatching.

At the time of hatching, activities of both KDH and succinate thiokinase increased in heart, while in liver only an enhanced activity of KDH was observed. Glutamate injected into egg exerted a stimulatory effect on KDH activity in chicken embryos but not in newborn chickens. There seems to be an age-dependent response of ASAT and GDH to stimulating effectors. In chicken embryos, 2-oxoglutarate induced GDH activity and in newly hatched chickens, ASAT activity. Concomitantly, liver protein content increased also. Administration of glutamate, however, was not followed by a significant activity increase of ASAT or GDH. Thus, the stimulation of ASAT and GDH activities seems to be favoured when they support glutamate formation out of 2-oxoglutarate.