Poly synthetase microsomal-ribosomal fraction

Table 1 shows the amount of enzyme units as well as the specific activity of poly-(ADP-ribose) synthetase in the different cell fractions of rat testis. These results show that a large proportion of enzyme is localized in the nuclear fraction and in the microsomal-ribosomal fraction. However, the specific activity of the enzyme was larger in the latter fraction. In contrast, the specific activity of the enzyme in the microsomal fraction of rat liver, brain, and kidney was negligible (Table 2). 

Fig. 2. Effect of DNAase I and RNAase on the activity of poly(ADP-ribose) synthetase. The microsomal-ribosomal fraction was preincubated at 25° C alone ( ), with RNAase (0 250 jug ml" ) or with DNAase I 250 jug ml" ). At the times indicated, aliquots were assayed for enzymatic activity...

Qermont and Perey [26] have shown that after birth, there is a good chronological relationship between the age of the rat and the type of spermatogenic cells present in the seminiferous tubules. This particular situation can be used to determine the type of spermatogenic cell in which poly(ADP-ribose) synthetase appears associated with the microsomal-ribosomal fraction. Accordingly, this cellular fraction was isolated from testis of rats at different time intervals after birth and the activity of the enzyme was measured. As shown in Table 4, the peak of activity was obtained with rats of 24- to 30-days-old. Thereafter, the specific activity of the enzyme reached the lower adult level. 

These results indicate that the maximal activity of poly(ADP-ribose) synthetase associated with the microsomal-ribosomal fraction of the testis was attained in rats... 

Our results demonstrate that by using cell fractionation procedures, it is possible to measure quite a significant level of poly(ADP-ribose) synthetase in the microsomal-ribosomal fraction of the testis and not in other somatic tissues. However, a major criticism to this experimental approach, is that the activity detected might well be due to a contamination with the nuclear enzyme. One fact that supports this criticism is that the nuclei contain a considerable amount of enzyme. On the other hand, no matter which procedure one uses to homogenize the tissue, the possibiUty of damaging the nucleus and consequently releasing some amount of enzyme, is difficult to discard. 

---

See also in sourсe #XX -- [ ]

---