Identification of the disulfide bonds of lysyl oxidase.

Proteolytic digestion of bovine aortic lysyl oxidase followed by tandem mass spectrometry has enabled assignment of all five disulfide bonds. The results indicate that the enzyme has a very stable central core containing three disulfide bonds, the lysyl tyrosyl quinone cross-link and the copper. This core is well isolated from solvent with the result that the oxidized (normal) form of the enzyme is remarkably resistant to proteolysis and is unusually stable at high temperatures and in the presence of denaturants.