Cytotoxic effect of conjugates of L-lysine alpha-oxidase with monoclonal antibodies on human tumor cell lines

The conjugates of L-lysine alpha-oxidase and monoclonal antibodies ICO-80 towards CD-5 receptor were produced using glutaraldehyde. The cytotoxic effect of conjugates on Yurkat cells line appeared to be lower in comparison with the native enzyme. Negligible decrease of conjugate biological activity may be explained by the large molecular weight of conjugate, which is several times higher than the molecular weight of the native enzyme. Such conjugates can not penetrate into the cells. So they catalyze the hydrogen peroxide formation, the main damaging agent, probably only outside the cells. We suppose also that the free native enzyme penetrates into the cell and activates there the oxidative deamination of L-lysine and correspondingly the hydrogen peroxide formation. This may be the proper explanation for the higher cytotoxic effect of L-lysinealpha-oxidase on Yurkat cell line.