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1. QUESTION: What is Proteinase K?
2. QUESTION: What is the function of proteinase K in DNA extraction?
In addition, there may be nucleases (enzymes that degrade nucleic acids) present. The addition of proteinase K degrades these nucleases and protects the nucleic acids from nuclease attack. In addition, proteinase K is stable over a wide pH range and is well suited for use in DNA extraction.
3. QUESTION: What are proteinase K applications?
ANSWER: Proteinase K is commonly used in molecular biology to digest protein and remove contamination from preparations of nucleic acid. Addition of Proteinase K to nucleic acid preparations rapidly inactivates nucleases that might otherwise degrade the DNA or RNA during purification. It is highly-suited to this application since the enzyme is active in the presence of chemicals that denature proteins, such as SDS and urea, chelating agents such as EDTA, sulfhydryl reagents, as well as trypsin or chymotrypsin inhibitors. Proteinase K is used for the destruction of proteins in cell lysates (tissue, cell culture cells) and for the release of nucleic acids, since it very effectively inactivates DNases and RNases. Some examples for applications: Proteinase K is very useful in the isolation of highly native, undamaged DNAs or RNAs, since most microbial or mammalian DNases and RNases are rapidly inactivated by the enzyme, particularly in the presence of 0.5 - 1% SDS. Purification of genomic DNA from bacteria (miniprep): bacteria from a saturated liquid culture are lysed and proteins are removed by a digest with 100 μg/ml Proteinase K for 1 h at 37 °C. The enzyme's activity towards native proteins is stimulated by denaturants such as SDS. In contrast, when measured using peptide substrates, denaturants inhibit the enzyme. The reason for this result is that the denaturing agents unfold the protein substrates and make them more accessible to the protease.
4. QUESTION: Why is proteinase K digestion performed at 50°C?
5. QUESTION: What are temperatures proteinase k inactivated?
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