Which agent is used to degrade proteins during DNA extraction?
Proteinase K is a broad-spectrum serine protease widely used during DNA extraction to digest proteins, including nucleases, histones, and cellular structural proteins. It exhibits high activity in presence of SDS and EDTA and at elevated temperatures around 50-65°C, conditions that simultaneously lyse cells and denature substrates. By hydrolyzing peptide bonds, it deproteinizes DNA, inactivates DNases and RNases, and improves yield and purity. RNase specifically degrades RNA, DNase degrades DNA, and Triton X-100 is a non-ionic detergent for membrane permeabilization, not for proteolysis.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.