Deoxyribonuclease in sea urchin embryos. Comparison of the activity present in developing embryos, in nuclei, and in mitochondria

Alkaline deoxyribonucleases (DNAse) have been studied in homogenates of Paracentrotus lividus embryos at different stages of development using polyacrylamide disc gel electrophoresis. The electrophoretic pattern, consisting of two bands of DNAse activity, does not change throughout development. Moreover, a comparison of the thermal inactivation kinetics and of the effect of divalent cations on the degradation of native and denatured DNA indicates that the same type of DNAse activity is present during development. Nuclear and mitochondrial extracts contain DNAse with a specific activity 4–5 times higher than that present in the whole-embryo homogenates. The enzymes from the two sources, however, do not differ remarkably, as is shown by the similarity of the electrophoretic pattern and by the behaviour in the presence of divalent cations. Analysis of the digestion products shows that both nuclear and mitochondrial extracts bring about endonucleolytic degradation of DNA used as substrate.