Molecular cloning and sequencing of two cDNAs encoding cathepsin L-related cysteine proteinases in the nervous system and in the stomach of the Norway lobster (Nephrops norvegicus).

Two cathepsin L-related cysteine proteinase molecular clones were isolated from cDNA libraries of mRNA from the eyestalk nervous system and the stomach of Nephrops norvegicus and sequenced. The cDNA from nervous system was first obtained by screening an eyestalk cDNA library with an oligonucleotide whose sequence derived from the amino acid sequence of a peptide isolated previously and subsequently with the 5' end of the longest cDNA probe thus obtained. Several clones were isolated and analysed: one of these clones contains the complete cDNA (NCP1:AC = X80989). It encodes a preproenzyme of 324 amino acid residues, and a putative mature enzyme of 217 residues. Only one variant (with one amino acid change) was identified. The screening of the stomach cDNA library was carried out with a cDNA probe corresponding to the 5' terminal region of the nervous system cysteine proteinase cDNA previously obtained. A near full-length cDNA (NCP2:AC = X80990) was isolated. The sequence for mature stomach cathepsin L-related cysteine proteinase is 215 residues long. Nervous system cathepsin L-like NCP1 is very similar to the American lobster cysteine proteinase LCP1 (81% identity) and the stomach cathepsin L-related NCP2 is very similar to cysteine protease LCP3 (82% identity). Moreover, comparison of the two Nephrops norvegicus cathepsin L-related cysteine proteinases revealed only 68% identity.