mannosidase

Mannosidases are enzymes that catalyze the hydrolysis of glycosidic bonds that contain a mannose residue. They remove terminal or internal mannose units from glycans and mannan-containing polysaccharides, thereby contributing to the processing and degradation of glycoproteins and plant cell wall components. Mannosidases occur in many organisms, including bacteria, fungi, plants, and animals.

The enzyme family includes alpha-mannosidases and beta-mannosidases, which cleave different types of linkages and substrate contexts. In many eukaryotes, multiple mannosidases reside in the lysosome, Golgi apparatus, or cytosol, reflecting diverse roles in glycan maturation, quality control of glycoproteins, and catabolic pathways. They are classified into several glycoside hydrolase families, reflecting structural diversity and mechanistic variation.

In humans, lysosomal alpha-mannosidase plays a key role in the degradation of N-linked glycoproteins. Deficiency of this enzyme causes alpha-mannosidosis, a rare lysosomal storage disorder characterized by neurodevelopmental impairment, motor abnormalities, skeletal and facial features, hearing loss, and immune system involvement. The condition varies in severity and age of onset.

Beyond human biology, mannosidases are important in biotechnology and research for the processing of glycoproteins and for the degradation of plant mannans. They contribute to nutrient cycling in ecosystems and are studied for their substrate specificities, regulatory roles, and potential applications in medicine and industry.