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Serine proteases (or serine endopeptidases) are enzymes that cleave peptide bonds in proteins. Serine serves as the nucleophilic amino acid at the (enzyme's) active site. [1] They are found ubiquitously in both eukaryotes and prokaryotes. Serine proteases fall into two broad categories based on their structure: chymotrypsin-like (trypsin-like ...
1969 – Subtilisin (PDB file 1sbt [23]) was a second type of serine protease with a near-identical active site to the trypsin family of enzymes, but with a completely different overall fold. This gave the first view of convergent evolution at the atomic level.
Serpins are a superfamily of proteins with similar structures that were first identified for their protease inhibition activity and are found in all kingdoms of life. [1] [2] The acronym serpin was originally coined because the first serpins to be identified act on chymotrypsin-like serine proteases (serine protease inhibitors).
The venom of solenodons and some shrews like the northern short-tailed shrew consist of multiple copies of kallikrein 1 (KLK1) serine proteases. [3] KLK1 are very similar to serine protease found in venomous snakes like vipers, and have evolved in parallel from a common toxin precursor, [4] which cause hypotensive effects in vivo. [5]
Similarly, RHBDF1 is a homolog of the S54 family rhomboid proteases with an alanine in the place of the nucleophilic serine. [ 74 ] [ 75 ] In some cases, pseudoenzymes may still have an intact catalytic triad but mutations in the rest of the protein remove catalytic activity.
They appear to have independently and convergently evolved an Asp/Ser/His catalytic triad, like in the trypsin serine proteases. The structure of proteins in this family shows that they have an alpha/beta fold containing a 7-stranded parallel beta sheet. The subtilisin family is the second largest serine protease family characterised to date.
Conversely, the individual families that make up a superfamily are defined on the basis of their sequence alignment, for example the C04 protease family within the PA clan. Nevertheless, sequence similarity is the most commonly used form of evidence to infer relatedness, since the number of known sequences vastly outnumbers the number of known ...
Chymases (EC 3.4.21.39, mast cell protease 1, skeletal muscle protease, skin chymotryptic proteinase, mast cell serine proteinase, skeletal muscle protease) are a family of serine proteases found primarily in mast cells, though also present in basophil granulocytes (e.g. alpha chymase mcpt8).