Polymorphism and evolution of collagenolytic serine protease genes in crustaceans

Two genomic DNA fragments encoding crustacean collagenolytic serine proteas e genes show coding fragments that span 1522-1526 base pairs and contain se ven exons encoding the complete amino acid sequence of two enzymes, CHYA an d CHYB. As in serine protease genes from other organisms, the region coding for the residues around the active site is split by two introns. Although the introns differ from those of other organisms in size and nucleotide seq uence, their number and location are more or less the same as found in mamm alian chymotrypsin or elastase genes that evolved lately, but different for trypsin genes. Meanwhile, the junction that occurs between the propeptide and the maturation site is only found in the shrimp genes. This is also the case for the junction located 13 amino acids after the active site asparti c acid in these genes. Between 40 and 50 copies of the genes are reported b y Southern analysis. Seven different genes within ChyA Pv family present 0- 6% base changes, whereas five different genes belonging to ChyB Pv family s how changes of up to 27% in the short studied portion of exon 4. This last family presents a mosaic organization of the coding parts, which are also e xpressed in the hepatopancreas of the shrimp as the variant PVC5 cDNA. (C) 1999 Elsevier Science B.V. All rights reserved.