[Metabolic pathway of the degradation of macromolecules by lysosomal enzymes]

The lysosomes of most cells function principally in intracellular digestion. They contain several dozens of enzymes, mostly acid hydrolyases. Vacuolar-ATPase on lysosomal membrane establishes low-pH environment required for efficient expression of hydrolyase activity. Of several dozen disorders of human and various animals known to be due to lysosomal dysfunctions, most of the lysosomal storage diseases are of genetic origin. Metabolic pathways of intracellular macromolecules within lysosomes have been established from studies on the molecular and biochemical defects on lysosomal enzymes. In the lysosomal storage diseases most of all, the metabolic pathways of breakdown of lipids, glycosaminoglycans or oligosaccharides are severely affected. The degradation pathways of glycoproteins, proteoglycans, and glycolipids by lysosomal enzymes are described in this brief review.