Poly(ADP-ribose) Synthetase Associated to Cytoplasmic Structures of Meiotic Cells
An active poly(ADP-ribose) synthetase has been found to be associated to mitochondria of frog oocytes and of testis from various species. The enzyme was also found in association with the microsomal-ribosomes fraction of the testis. Both enzymes are strongly inhibited by nicotinamide, thymidine, and theophylline, and they synthesize oligomers of ADP-ribose of an average chain length of 2-6 residues. The apparent K m. for NAD+ of the mitochondrial enzyme is 22 µ m which contrasts with the corresponding value of the chromatin-bound enzyme, 210 µ m NAD+. Treatment of the isolated mitochondria with Triton X-100 revealed that the enzyme is associated to a polydisperse structure. The higher specific activity of the enzyme associated to mitochondria was found in testis of 20 to 30 days old rats. This development study suggests that the maximal activity of the enzyme is associated to mitochondria belonging to primary spermatocytes.
Poly(ADP-ribose) synthetase was also found in association of the microsome-ribosome fraction of rat, mouse, carp, and bull testis. This activity is 20 to 30 times higher than in the same fraction of the liver. Contrary to the chromatin-bound enzyme, the microsome-ribosome enzyme activity is stimulated 3 to 4 times by DNA, but it is slightly inhibited by histone H 1. The enzyme seems to be associated to ribo-nucleoproteins of a very polydisperse nature. The possible relationship of poly(ADP-ribose) synthetase with the intermitochondrial cement and with the chromatoid body will be discussed. These are very unique structures only present in germinal cells.