CTSA, also known as lysosomal protective protein isoform b, is a component of the lysosomal multienzyme complex along with beta-galactosidase and sialidase Neu1. It is a multicatalytic enzyme with deamidase and esterase in addition to carboxypeptidase activities. Recombinant mouse CTSA, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.