Expression of active, human lysyl oxidase in Escherichia coli.

Lysyl oxidase (LO) is a copper amine oxidase of the extracellular matrix which initiates covalent cross-linking in collagens and elastin. Human LO was expressed in Escherichia coli. At 37°C, large amounts of protein were obtained, but in the form of insoluble aggregates. Lowering the growth temperature, and reducing the amount of inducer, resulted in the production of soluble LO, which was active on a [3H]lysine-labeled elastin substrate. LO was also targeted to the periplasm as a fusion protein with the pelb signal peptide. The periplasmic enzyme was soluble, active and inhibited by β-aminopropionitrile. Production of the carbonyl co-factor is therefore not a limitation in the expression of active LO in bacteria.