Staining electrophoretic gels for laccase and peroxidase activity using 1,8-diaminonaphthalene

A new chromogenic substrate for laccases and peroxidases, 1,8-diaminonaptha lene, was used to detect phenoloxidase activity in gels after SDS-PAGE. Thi s substrate has several advantages over other widely used phenoloxidase sta ins in that it is inexpensive, and the oxidized product has both high molar absorptivity and very low solubility. Furthermore, neither the substrate n or the product is known to have toxicity problems of the type associated wi th many other phenoloxidase stains. The sensitivity of detection using 1,8- diaminonapthalene was comparable to that obtained using the most sensitive stains commonly used for phenoloxidases, e.g., 3,3-diaminobenzidine, and wa s close to that attainable for protein detection using silver staining. Zym ograms developed with 1,8-diaminonapthalene can be used with video densitom etry to monitor the specific enzymatic activity of phenoloxidases during en zyme purification. (C) 2001 Academic Press.