Oxidation of epsilon-amino group of lysyl peptides by bovine serum amine oxidase.

We examined whether bovine serum amine oxidase (BSAO) was able to oxidize lysyl peptides. Seven synthetic peptides, Z-Lys-Leu-OMe, Z-His-Lys-Leu-OMe, Z-Val-Leu-Gly-Lys-Leu-OMe, Ala-Ala-Lys, Ala-Lys-Ala, Phe-Lys, and Gly-Lys were incubated with BSAO at 37 degrees C for 4 days, and the extent of oxidation (H2O2 formation) was assayed by o-dianisidine method. The amino acid sequence of lysyl peptides affected the oxidation rate by BSAO. The rate of oxidation of Z-Lys-Leu-OMe was about fifty fold higher than that of Z-His-Lys-Leu-OMe. Z-Lys-Leu-OMe, the lysyl peptide most reactive with BSAO was analyzed by the 3-methyl-2-benzothiazolinone hydrochloride method, amino acid analysis, and the 2,4,6-trinitrobenzene sulfonic acid method. The production of aldehyde, a decrease in the lysine/leucine ratio, and a decrease in epsilon-amino group were confirmed. These results show that bovine serum amine oxidase is able to oxidize the epsilon-amino group of lysyl peptides.