Abstract
Serine proteases constitute the major protein content of mast cell (MC) secretory granules. These proteases can generally be subdivided into chymases and tryptases based on their primary cleavage specificity. Here, we presented the extended cleavage specificities of a rabbit β-chymase and a guinea pig α-chymase. Analyses by phage display screening and a panel of recombinant substrates showed a marked similarity in catalytic activity between the enzymes, both being strict Leu-ases (cleaving on the carboxyl side of Leu). Amino acid sequence alignment of a panel of mammalian chymotryptic MC proteases and 3D structural modeling identified an unusual residue in the rabbit enzyme at position 216 (Thr instead of more common Gly), which is most likely critical for the Leu-ase specificity. Almost all mammals studied, except rabbit and guinea pig, express classical chymotryptic enzymes with similarly extended specificities, indicating an important role of chymase in MC biology. The rabbit and guinea pig are the only two mammalian species currently known to lack a classical MC chymase. Key questions are now how this major difference affects their MC function, and if genes of other loci can rescue the loss of a chymotryptic activity in MCs of these two species.
Highlights
Mast cells (MCs) are innate hematopoietic cells distributed primarily at the interphase between the host and the environment
Analysis of the β-chymases, rat mast cell proteases, and mouse mast cell protease 4, by phage display shows that these proteases prefer Phe or Tyr at the P1 position, indicating that β-chymases became the primary chymotryptic enzymes in rodents when the function of the α-chymases changed to elastases [8,9]
By using a combination of a panel of different methods, including phylogenetic analyses, phage display, cleavage of recombinant and chromogenic substrates, alignments of primary structures, and 3D structural predictions, here we presented a detailed picture of the rabbit: Cma1-like protein concerning its enzymatic activity, substrate selectivity structure, and evolutionary relationship to other mammalian MC chymases
Summary
Mast cells (MCs) are innate hematopoietic cells distributed primarily at the interphase between the host and the environment. Analysis of the β-chymases, rat mast cell proteases (rMCP-1 and rMCP-4), and mouse mast cell protease 4 (mMCP-4), by phage display shows that these proteases prefer Phe or Tyr at the P1 position, indicating that β-chymases became the primary chymotryptic enzymes in rodents when the function of the α-chymases changed to elastases [8,9]. Attempts to clone the β-chymase cDNA by PCR amplification with specific primers designed from the 2015 genome sequence release, using RNA from different dog tissues have failed, indicating that the gene may not be active and, should be considered a pseudogene [10]. By using a combination of a panel of different methods, including phylogenetic analyses, phage display, cleavage of recombinant and chromogenic substrates, alignments of primary structures, and 3D structural predictions, here we presented a detailed picture of the rabbit: Cma1-like protein concerning its enzymatic activity, substrate selectivity structure, and evolutionary relationship to other mammalian MC chymases. We compared the rabbit enzyme with the guinea pig β-chymase, which showed a remarkably similar cleavage specificity as the rabbit enzyme, indicating convergent evolution by αand β-chymases, highlighting a potentially new set of in vivo substrates
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
