A PROTEIN INHIBITOR OF ACID DEOXYRIBONUCLEASES

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Abstract
A protein extracted and partially purified (about 100-fold) from mouse liver is able to inhibit the acid DNases from different tissues and species, whereas pancreatic DNase and E. coli endonuclease I are not inhibited. The acid DNase displays typical Michaelis-Menten kinetics in the absence of this inhibitor, but the kinetics become sigmoidal in its presence. The existence of a DNase-inhibitor complex is demonstrated by physicochemical experiments. Moreover, the inhibitor is able to reactivate the DNase treated by urea, probably through a reassociation of the inactive monomers to a dimeric state. An allosteric model in which the DNase-inhibitor complex is composed of catalytic (DNase) and regulatory (inhibitor) subunits could explain these data.
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