A Deoxyribonuclease from Chlamydomonas reinhardii. 1. Purification and Properties

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Abstract
A DNase [EC 3.1.4.5] was purified more than 2000-fold from the green alga, C. reinhardii. The enzyme is most active on denatured DNA. Optimum activity is at pH 8.5, in 80 mM Tris-HCl buffer and 2 mM CaCl2. Other divalent cations can replace Ca2+ with varying lower efficiency. EDTA and Pi are strongly inhibitory, while ATP and high concentrations of 2-mercaptoethanol are slightly inhibitory. The MW is approximately 35,000, the Stokes radius is 2.7 nm, and the sedimentation coefficient 2.8 S. It is a single polypeptide chain, and the frictional ratio of 1.27 suggests it is only slightly asymmetrical. The isoelectric point is 9.5. This enzyme was termed exonuclease 1.