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Purification and Properties of Double-Stranded RNA-Specific Adenosine Deaminase from Calf Thymus
Mary A. O'Connell and Walter Keller
Proceedings of the National Academy of Sciences of the United States of America
Vol. 91, No. 22 (Oct. 25, 1994), pp. 10596-10600
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/2366076
Page Count: 5
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A double stranded RNA-specific adenosine deaminase, which converts adenosine to inosine, has been purified to homogeneity from calf thymus. The enzyme was purified ≈340,000-fold by a series of column chromatography steps. The enzyme consists of a single polypeptide with a molecular mass of 116 kDa as determined by electrophoresis on a SDS/polyacrylamide gel. The native protein sediments at 4.2 s in glycerol gradients and has a Stokes radius of 42 Å upon gel-filtration chromatography. This leads to an estimate of ≈74,100 for the native molecular weight, suggesting that the enzyme exists as a monomer in solution. Enzyme activity is optimal at 0.1 M KCl and 37⚬C. Divalent metal ions or ATP is not required for activity. The Km for double-stranded RNA substrate is ≈7 x 10-11 M. The Vmax is ≈10-9 mol of inosine produced per min per mg and the Kcat is 0.13 min-1.
Proceedings of the National Academy of Sciences of the United States of America © 1994 National Academy of Sciences