Serine proteases (or serine endopeptidases) are enzymes that cleave peptide bonds in proteins, in which serineserves as the nucleophilic amino acid at the (enzyme’s) active site. They are found ubiquitously in both eukaryotes andprokaryotes. Serine proteases fall into two broad categories based on their structure: chymotrypsin-like (trypsin-like) orsubtilisin-like. In humans, they are responsible for co-ordinating various physiological functions, including digestion, immune response, blood coagulation and reproduction.