Both enzymes belong to the trypsin family of serine proteases and both have a substrate specificity for argynyl and lysyl residue-containing substrates. I know that PAR 2 has a SKGR34↓S35SLIGKV cleavage site, making it possible for both trypsin and tryptase to cleave after R. But PAR1 cleavage site LDPR41↓S42FLLRN, also contains a R just as PAR4 its cleavage site PAPR47↓G48 YPGQV... So why can only trypsin and thrombin cleave here and not tryptase?
I think that tryptase shows specificity for the next amino acid after the basic one. It shows certain specificity for N, other basic (K,R) and P. Anyway, Glycine48 is a very poor residue for tryptase. See Harris et al., JBC, 2001
It has been postulated that it is steric hindrance that prevents tryptase from acccessing the cleave site. The active enzyme site of tryptase is located on the inward facing surface of the structure created by its four subunits, unlike the enzymatic sites of trypsin and other serine proteases. See the posted model of its crystal structure at the NIH site.
- Badges
- Science topic
- Similar topics
- Biological Science
- Biochemistry
- Enzymology