Lysyl oxidase coupled with catalase in egg shell membrane

The activity of lysyl oxidase was found in egg shell membrane (ESM) of hens. The activity was determined by measuring the enzymatic conversion of n-butylamine and N alpha-acetyl-L-lysine to n-butyraldehyde and N alpha-acetyl-L-allysine, respectively. ESM lysyl oxidase was significantly inhibited by beta-aminopropionitrile, chelating agents, and deoxygenation, consistent with the known properties of lysyl oxidase. Nevertheless, ESM lysyl oxidase was insoluble in urea solution, suggesting that it complexes with ESM. These findings support previous reports indicating the presence of lysine-derived cross-links in ESM and the necessity of lysyl oxidase located in the isthmus of the hen oviduct for the biosynthesis of ESM. Lysyl oxidase secreted around the egg white from the isthmus may initiate the cross-linking reaction of ESM protein, and remain as the constituent of ESM. Moreover, the H2O2 released by lysyl oxidase in ESM was completely decomposed by coexisting catalase activity. ESM lysyl oxidase activity was greatly elevated in the presence of H2O2, probably due to the O-2 produced by catalase. These findings indicate that lysyl oxidase is coupled with catalase in ESM. This coupling enzyme system was considered to be involved in the biosynthesis of ESM and to protect the embryo against H2O2. (C) 1999 Elsevier Science B.V. All rights reserved.