Distribution intracellulaire de l'exonucléase acide dans le foie de rat.

Acid exonuclease activity of rat liver has been determined with the help of DNA core as substrate, The intracellular distribution of the enzyme has been investigated by differential centrifugation of homogenates and compared with those of cytochrome oxidase, acid phosphatase and glucose-6-phosphatase used as reference enzymes for mitochondria, lysosomes and endoplasmic reticulum respectively. Acid exonuclease is principally associated with mitochondrial fractions and exhibits a distribution pattern similar to that of acid phosphatase. After isopyenic centrifugation in a sucrose gradient of a total mitoehondrial fraction, acid exonuclease like acid phosphatase shows a relatively flattened distribution curve with a median equilibrium density of about 1.2. The injection to the rat of Triton WR -1339, which lowers the equilibrium density of lysosomal enzymes has a similar effect on acid exonuclease. Acid exonuclease exhibits the phenomenom of structurelinked latency. it is concluded that acid exonuclease is associated with the lysosomes in rat liver. Separation between acid DNase and acid exonuelease associated with lysosomes can be performed by chromatography on hydroxyapatite of an extract of purified granules. The complementary action of the two enzymes in lysosomal digestion of DNA is illustrated, [ABSTRACT FROM AUTHOR]