EC Number   |
Natural Substrates |
|---|
   3.5.4.B9 | cytosine in single-stranded viral DNA + H2O |
the enzyme targets 5'-CCCA-3' sequences with 5'-AAACCCAAA-3' recognized most efficiently |
| 3.5.4.B9 | cytosine in single-stranded viral DNA + H2O |
the full-length enzyme processively deaminates cytidine in two 5'-CCC-3' motifs located on a single-stranded DNA substrate, during one binding event. The full-length enzyme also exerts a 3' to 5' deamination bias by preferentially deaminating the cytidine in the CCC motif near the 5'end of the single-stranded DNA substrate |
| 3.5.4.B9 | cytosine in single-stranded viral DNA + H2O |
the APOBEC3 enzymes are a double-edged sword that can catalyze deamination of cytosine in genomic DNA, which results in potential genomic instability due to the many mutagenic fates of uracil. The enzymes must be able to efficiently deaminate transiently available single-stranded DNA during reverse transcription, replication, or transcription. Specific biochemical characteristics promote deamination in each situation to increase enzyme efficiency through processivity, rapid enzyme cycling between substrates, or oligomerization state |
| 3.5.4.B9 | deoxycytosine in single-stranded viral DNA + H2O |
- |
| 3.5.4.B9 | more |
the enzyme binds randomly to single-stranded DNA, then jumps and slides processively to deaminate target motifs. Preferential deamination of the third C is observed in the motif 5'-AAACCCAAA-3' while deamination at the first C is not observed. The replacement of AAA with TTT at the 3' side of CCC results in a 20fold inhibition of deamination. The replacement of AGA by TTT at the 5' side of CCC results in about a 5fold reduction in specific activity. Similar binding constants are observed with single-stranded DNA substrates ranging from 10 to 69 nucleotides whereas binding is reduced sharply for a 9-nucleotide substrate. When confronting partially double-stranded DNA, to which the enzyme cannot bind, sliding is lost but jumping is retained. The enzyme shows catalytic orientational specificity such that deamination occurs predominantly 3'-5' without requiring hydrolysis of a nucleotide cofactor |
| 3.5.4.B9 | more |
the enzyme binds with similar efficiency to the 5' and 3' single-stranded DNA substrates and binds the single-stranded region of the gap-DNA substrates with the same efficiency as tail-DNA. Enzyme monomers, dimers, and higher-order oligomers can bind single-stranded DNA substrates in a manner independent of strand polarity and availability of free single-stranded DNA ends. The efficiency of complex formation decreases about 3 times for the 18single-stranded-tail-DNA compared to that for the longer 69single-stranded-tail-DNA hybrid substrate |
| 3.5.4.B9 | more |
the enzyme deaminates C -> U on single-stranded DNA, but favors 5'CCCC target motifs with a preference for the 3'C, and its specific activity is strongly influenced by nucleotides surrounding the 5'CCC target motif |
| 3.5.4.B9 | more |
the enzyme does not effectively bind substrates shorter than 10 nucleotides. Substrates containing 5'-methyldeoxycytidine 2'-deoxy-5-aza-5,6-dihydrocytidine, 2'-deoxy-4-ethylcytidine and 2'-deoxyzebularine at position -1 are deaminated by the enzyme with 62%, 25%, 19%, and 9% efficiency, respectively, Substrates containing N3-methyl cytidine or isocytidine at position -1 are not appreciably deaminated by the enzyme |
| 3.5.4.B9 | more |
the enzyme has a catalytically inactive N-terminal CD1 domain that mediates processivity and an active C-terminal CD2 domain that catalyzes deaminations. The enzyme cannot bind well to double-stranded DNA. Native enzyme is still able to processively deaminate two C residues with a double-stranded DNA region in-between, but with a 2fold decrease in the processivity factor |
