Dpn I

Isoschizomers
The enzyme is an isoschizomer to Bsp143 I, Dpn II, Mbo I, Nde II and Sau3A I.
Methylation sensitivity
The enzyme is only inhibited by the occurrence of 5-methylcytosine at the indicated site (*) if no 6-methyladenine is present.
Typical ligation and recutting assay
Dpn I fragments obtained by complete digestion of 1μg pBR322 DNA are ligated for 16 hours at +4°C with 1U T4 DNA Ligase in 10μl buffer that contains 66mM Tris-HCl, 5mM MgCl₂, 5mM Dithiothreitol, 1mM ATP, pH 7.5 (at +20°C). The percentages of product that can be ligated and subsequently recut with Dpn I (yielding the typical pattern of pBR322 × Dpn I fragments) are stated under "Lig" and "Rec" in the certificate of analysis.

Dpn I requires methylation of adenine residues for activity and thus digests only G^mATC sequences containing N6-methyladenine. Such methylated sequences are produced by dam methylase. This requirement for methylation distinguishes Dpn I from Mbo I, which is inhibited by dam methylation, and Sau3A I, which is not influenced by dam methylation. Dpn I also cleaves at a different position on the recognition sequence than Mbo I and Sau3A I.

Recognition sites: GmAT*C
G^mAT*C
Restriction site: GmA↓T*C
G^mA↓T*C
Heat inactivation: No inactivation of Dpn I after incubation at 65 °C for 15 minutes.

In PCR-mediated mutagenesis, DpnI nuclease has been used for the digestion of wild type DNA after PCR.[1]

Absence of nonspecific endonuclease activities
1μg pBR322 DNA is incubated for 16 hours in 50μl SuRE/Cut Buffer A with an excess of Dpn I. The number of enzyme units which do not change the enzyme-specific pattern is stated in the certificate of analysis.
Absence of exonuclease activity
Approximately 5μg [³H] labeled calf thymus DNA are incubated with 3μl Dpn I for 4 hours at +37°C in a total volume of 100μl 50mM Tris-HCl, 10mM MgCl₂, 1mM Dithioerythritol, pH approximately 7.5. Under these conditions, no release of radioactivity is detectable, as stated in the certificate of analysis.

Number of cleavage sites on different DNAs

• λ: 116
• φX174: 0
• Ad2: 87
• M13mp7: 8
• pBR322: 22
• pBR328: 27
• pUC18: 15
• SV40: 8

One unit is the enzyme activity that cleaves 1 μg pBR322 DNA in one hour at +37 °C in a total volume of 25 μl (1x) SuRE/Cut Buffer A. Since complete Dpn I digestion of pBR322 DNA needs fully methylated GATC sequences < 5% partial digested bands may be observed during activity determination.

SuRE/Cut Buffer System
The buffer in bold is recommended for optimal activity

• A: 100%
• B: 75-100%
• H: 75-100%
• L: 50-75%
• M: 75-100%

Activity in PCR buffer: 100%

Relative activity in PCR mix (Taq DNA Polymerase buffer) is 100%. The PCR mix contained λDNA, primers, 10 mM Tris-HCl (pH 8.3, 20 °C), 50 mM KCl, 1.5 mM MgCl₂, 200 μM dNTPs, 2.5 U Taq DNA polymerase. The mix was subjected to 25 amplification cycles.Activity in reaction buffer of Pwo SuperYield DNA Polymerase PCR Mix is 100%; Pwo SuperYield DNA Polymerase PCR Mix is not available in U.S.

Dpn I generates fragments with blunt ends that are compatible with any blunt end.
For life science research only. Not for use in diagnostic procedures.