An antibacterial V V11 kDa protein designated chlamysin was isolated from viscera of the marine bivalve Chlamys islandica. Chlamysin inhibited the growth of all Grampositive and Gram-negative bacteria tested. The isolated protein was highly efficient in hydrolyzing Micrococcus luteus cells only at low pH (4.5^6.2) and at low temperature (4^35³C). No significant loss of enzyme activity was observed after 30 days storage at room temperature or after heating to 70³C for 15 min, suggesting relatively high protein structure stability. Sequenceanalyzed fragments of the protein revealed data which guided the isolation of the cDNA gene, encoding a 137 amino acid chlamysin precursor in scallops. The deduced protein contains a high portion of cysteine, serine and histidine residues and has a predicted isoelectric point below 7. The chlamysin protein was found to have sequence homology to an isopeptidase and to a recently published bivalve lysozyme.z 1999 Federation of European Biochemical Societies.

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The Atlantic salmon (Salmo salar) goose-type lysozyme gene was isolated and revealed alternative splicing within exon 2 affecting the signal peptide-encoding region. The lysozyme was produced in Escherichia coli, and the recombinant enzyme showed a high specific lytic activity that was stimulated by low or moderate concentrations of mono- or divalent cations. Relative lytic activities of 70 and 100% were measured at 4 degrees C and 22 degrees C, respectively, and there was no detectable activity at 60 degrees C. However, 30% activity was retained after heating the enzyme for 3 h at 90 degrees C. This unique combination of thermal properties was surprising since the salmon goose-type lysozyme contains no cysteines for protein structure stabilization through disulphide bond formation. The results point to a rapid reversal of inactivation, probably due to instant protein refolding.

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