Influence of Glucosylation of Deoxyribonucleic Acid on Hydrolysis by Deoxyribonucleases of Escherichia coli

From the ¹ From the Department of Biological Chemistry, Harvard Medical School, Boston, Massachusetts 02115

1. The influence of glucosylation of deoxyribonucleic acid on the hydrolysis by the four deoxyribonucleases of Escherichia coli has been described.

2. Exonuclease II, the nuclease associated with DNA polymerase, and exonuclease III (DNA phosphatase-exonuclease) hydrolyze DNA from T-even bacteriophages at less than 5% the rate of T7 DNA. Exonuclease I and endonuclease I hydrolyze T-even deoxyribonucleic acids at only slightly diminished rates compared to those observed with T7 DNA.

3. DNA isolated from T*2 or T*6 bacteriophages contains hydroxymethylcytosine in place of cytosine but is deficient in glucose. T*2 and T*6 deoxyribonucleic acids are degraded by exonuclease III at rates approximately 20-fold greater than those found for T2 and T6 DNA. Glucosylation of T*2 DNA by UDP-glucose and by the T2 -glucosyltransferase converts T*2 DNA into a substrate which is hydrolyzed at the diminished rates found for normal T2 DNA.

4. The phosphatase activity of exonuclease III is not significantly influenced by glucosylation of the DNA substrates.

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