Overproduction and properties of the mannuronate alginate lyase AlxMB

Abstract In previous studies (Malissard et al., FEMS Microbiol. Lett. (1993) 110, 101–106), the alginate lyase AlxM of the marine bacterium ATCC 433367 was produced in Escherichia coli TC4/pAL-A3 with a yield of 50 μg per litre of culture. The polypeptide chain was cleaved between two cysteine residues, C169 and C183, themselves linked by a disulphide bridge. AlxM has now been overproduced in E. coli BL21(DE3)/pAL-Sur/pLysS. Under conditions in which formation of inclusion bodies can be avoided, the enzyme is synthesized as a catalytically active, water-soluble, unnicked polypeptide with a yield of 32 mg per litre of culture. It has been purified to protein homogeneity using a one-step procedure. The nicked AlxM_A and unnicked AlxM_B alginate lyases have identical alginate-degrading activities at high salt concentrations.