[AMP-aminohydrolase activity of the nuclear fraction of rat brain].

AMP-aminohydrolase activity has been found not only in mitochondrial and soluble fractions but also in nuclear fraction of rat brain. The regulation of nuclear AMP-aminohydrolase activity differs from that of mitochondrial and soluble fractions. 1. Hexokinase does not enhance deamination of AMP in intact nuclei while it activates the enzyme in extracts of acetone powder of nuclear fractions. 2. The AMP-aminohydrolase activity of rat brain nuclear fraction is considerably inhibited by GTP and phosphate but in contrast to other fractions the stimulatory effect of ATP on enzyme activity is preserved.