Proteinase K is a serine protease that belongs to the subtilisin family. It has extremely high enzyme activity and wide substrate specificity. It can preferentially decompose the ester bonds and peptide bonds adjacent to the C-terminus of hydrophobic amino acids, sulfur-containing amino acids, and aromatic amino acids. It is often used to degrade proteins to produce short peptides. It has the typical catalytic triad Asp39-His69-Ser224 characteristics unique to serine proteases, and there are two Ca2+ binding sites around the active center to increase its stability, allowing it to maintain high enzyme activity under more extensive conditions.