Deoxyribonuclease II

I.U.B.: 3.1.22.1
Deoxyribonucleate 3'-oligonucleotidohydrolase

Enzymatic Reaction (image will open in a new window) 

Deoxyribonuclease II (Acid DNase) hydrolyzes deoxyribonucleotide linkages in native and denatured DNA yielding products with 3'-phosphates. In vitro, its optimum pH range is 4.5 - 5.0. It also acts upon p-nitrophenyl-phosphodiesters at pH 5.6 - 5.9 (Bernardi and Griffe 1964). In a review Bernardi (1971) describes three phases in the degradation of native DNA by acid DNase. The enzyme is a glycoprotein with trimeric structure (Bernardi et al. 1965). It has been postulated that the active site on each subunit would account for the "single-hit" mechanism described by Bernardi and Sadron (1964) whereby both strands of DNA are cleaved simultaneously.

Acid DNases are widely found in animal cells, mostly in lysosomes. It might be noted that Slor et al. (1973) found that peaks of DNase II activity coincide with peaks of DNA syntheses in cell cycles in synchronized HeLa S3 cell cultures.

Margison and O'Connor (1972) report that DNase activity is greatly reduced for methylated DNA.

Characteristics of Enzyme from Porcine Spleen: 

Molecular weight: 3.8 X 10⁴ (Bernardi et al. 1965).

Composition: Bernardi et al. (1965) report it to be a glycoprotein of dimeric structure with an active site on each subunit. They also indicate its amino acid analysis. Two components, A and B, have been separated chromatographically. (Bernardi et al. 1966). See Bernardi's review (1971).

Optimum pH: 4.5 - 5.0 at ionic strength 0.15 (Bernardi and Griffe 1964).

Extinction coefficient: = 12.1 (Bernardi et al . 1965).

Isoelectric point: 10.2 (Bernardi et al. 1965).

Specificity: Doskocil and Sorm (1961) indicate that the sequence Gp-Cp is preferentially attacked. See review article by Bernardi (1971) and later reports by Sicard et al. (1972), Soave et al. (1973) and Bernardi et al. (1975).

Inhibitors: Iodoacetic acid, N-bromosuccinimide and H₂O₂ are strongly inhibiting, but not diisopropylfluorophosphate (Melzer 1969). Bernardi and Griffe (1964) found sulfate to be inhibitory.