Catalyzes the removal of sialic acid (N-acetylneuraminic acid) moieties from glycoproteins and glycolipids. To be active, it is strictly dependent on its presence in the multienzyme complex. Appears to have a preference for alpha 2-3 and alpha 2-6 sialyl linkage. Hydrolysis of alpha-(2->3)-, alpha-(2->6)-, alpha-(2->8)- glycosidic linkages of terminal sialic acid residues in oligosaccharides, glycoproteins, glycolipids, colominic acid and synthetic substrates. Interacts with cathepsin A (protective protein), beta-galactosidase and N-acetylgalactosamine-6-sulfate sulfatase in a multienzyme complex. Localized not only on the inner side of the lysosomal membrane and in the lysosomal lumen, but also on the plasma membrane and in intracellular vesicles. Highly expressed in kidney, epididymis, followed by brain, spinal cord and weakly expressed in adrenal, heart, liver, lung and spleen. A C-terminal internalization signal (YGTL) appears to allow the targeting of plasma membrane proteins to endosomes. N-glycosylated. Phosphorylation of tyrosine within the internalization signal results in inhibition of sialidase internalization and blockage on the plasma membrane. Belongs to the glycosyl hydrolase 33 family.