Final answer:
Proteinase K serves to digest contaminating proteins in the extraction protocol, improving the quality and reproducibility of protein samples for analysis, especially when using high-resolution techniques like 2-DE.
Step-by-step explanation:
The enzyme Proteinase K is important in the protein extraction protocol because it digests proteins that can interfere with the extraction and analysis process. This proteolytic enzyme helps to remove contaminating proteins that can cause proteolytic breakdown, streaking, and smearing, which would otherwise result in lower quality results when analyzing protein samples from sources like soybean seeds. Proteinase K is particularly valuable when extracting proteins for analysis via high-resolution techniques such as two-dimensional polyacrylamide gel electrophoresis (2-DE), as it ensures that the results are reliable and the proteins can be resolved distinctly.