Lysosomal-associated membrane glycoprotein

O Souza MP, August JT. A kinetic analysis of biosynthesis and localization of a lysosome-associated membrane glycoprotein. Arch Biochem Biophys 1986 249(2) 522-532. 

W.C. Wang, N. Lee, D. Aoki, M.N. Fukuda and M. Fukuda, The poly-N-acetyllactosamines attached to lysosomal membrane glycoproteins are increased by the prolonged association with the Golgi complex. J. Biol. Chem., 266 (1991) 23185-23190. 

Interestingly, all of the enzymes that comprise the sphingolipid-catabolic pathway are glycoproteins and may be found in different places within the organelle. For example, glucocerebrosidase is firmly associated with the lysosomal membrane, whereas others, like hexoseaminidase A, exist largely in soluble form in the lysosomal matrix. A common property of the lysosomal hydrolases, however, is their expression of maximum activity at a relatively acidic pH (i.e., pH 4.0-5.5), hence the term acid hydrolase. This is not unexpected because ATP-driven proton pumps sustain an acidic milieu (pH 5.2) within the lysosome. 

The binding of large and small extracellular substances to receptors on cell surfaces, particularly the interactions with paramyxovirus and the functions of sialoglyco-proteins on erythrocyte membranes, has been reviewed. The roles of glycoproteins in the membranes of mitochondria, milk-fat globules, and lysosomes and the interactions of lectins associated with intracellular membranes have been discussed. ... 

In studies with other systems, Glick et al. (1971) found sialidase, active toward fetuin, to be enriched in the lysosomal fraction of L cells Tulsiani and Carubelli (1971) found sialidase, active toward sialyllactose, not only enriched in lysomes isolated from rat mammary glands, but also in the soluble fraction Gielen et al. (1973) found a membrane-bound sialidase in leukocytes that was very active toward glycoproteins in the leukocyte homogenate and Bosmann (1974) found sialidase activity associated with the plasma membranes of human erythrocytes. Recently, Kishore et al. (1975) have reported the presence of a sialidase in Golgi isolated from rat liver. 

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