Abstract.
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°C and 22°C, respectively, and there was no detectable activity at 60°C. However, 30% activity was retained after heating the enzyme for 3 h at 90°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.
Keywords. Atlantic salmon, immunity, lysozyme, goose-type, gene, protein, cold-active, thermal tolerance
Footnotes
Received 14 August 2007; received after revision 07 September 2007; accepted 12 September 2007