A convenient protein substrate for the determination of protease specificity: reduced and S-3-(trimethylated amino)propylated lysozyme.

Reduced lysozyme was alkylated with 3-bromopropyltrimethylammonium bromide to give reduced and S-3-(trimethylated amino)propylated lysozyme. It was soluble in a wide range of pH and is suitable as the protein substrate to determine protease specificity.