The catalytic activity of the serine proteases from the trypsin family is
provided by a charge relay system involving an aspartic acid residue hydrogen-bonded to a histidine, which itself is hydrogen-bonded to a serine. The
sequences in the vicinity of the active site serine and histidine residues are
well conserved in this family of proteases . A partial list of proteases
known to belong to the trypsin family is shown below.
Blood coagulation factors VII, IX, X, XI and XII, thrombin, plasminogen,
and protein C.
Complement components C1r, C1s, C2, and complement factors B, D and I.
Complement-activating component of RA-reactive factor.
Plasminogen activators (urokinase-type, and tissue-type).
Trypsins I, II, III, and IV.
Snake venom proteases such as ancrod, batroxobin, cerastobin, flavoxobin,
and protein C activator.
Collagenase from common cattle grub and collagenolytic protease from
Atlantic sand fiddler crab.
Blood fluke cercarial protease.
Drosophila trypsin like proteases: α, easter, snake-locus.
Drosophila protease stubble (gene sb).
Major mite fecal allergen Der p III.
All the above proteins belong to family S1 in the classification of peptidases
[2,E1] and originate from eukaryotic species. It should be noted that
bacterial proteases that belong to family S2A are similar enough in the
regions of the active site residues that they can be picked up by the same
patterns. These proteases are listed below.
Achromobacter lyticus protease I.
Lysobacter α-lytic protease.
Streptogrisin A and B (Streptomyces proteases A and B).
Streptomyces griseus glutamyl endopeptidase II.
Streptomyces fradiae proteases 1 and 2.
We also developed a profile specific for the S1 family that spans the complete
domain. In addition to proteases from the S1 family, this profile also detects
proteins that have lost active site residues and which are therefore no longer
catalytically active. Examples of such proteins are haptoglobin and protein Z.
If a protein includes both the serine and the histidine active site
signatures, the probability of it being a trypsin family serine protease is
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