Abstract
An intracellular nuclease inhibitor was 1270 times purified from a heat treated cell free extract of fresh mycelia of Aspergillus oryzae, by ammonium sulfate fractionation and chromatographies using DEAE-cellulose and Sephadex G-75. The purified sample of the inhibitor showed a UV absorption curve typical for protein, and it was inactivated by proteases such as chymotrypsin. The inhibitor stoichiometrically inactivated nuclease O (an intracellular nuclease of Asp. oryzae), forming an enzyme-inhibitor complex. But, it did not affect nuclease S1, RNase T1, RNase T2 or pancreatic RNase. The inhibitor was insensitive to 10-5M p-chloromercuribenzoate or 10-4M Pb2+. Molecular weights estimated by the method of Andrews were 23, 000 for the inhibitor, 47, 000 for nuclease O, and 82, 000 for the enzyme-inhibitor complex. The nuclease activity was recovered from the inactive complex by the action of chymotrypsin.
