Defective GLB1 does not hydrolyse a glycosaminoglycan

Stable Identifier
Reaction [transition]
Homo sapiens
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Defects in beta-galactosidase (GLB1, MIM:611458) result in galactose moieties not being hydrolysed from keratan sulfate (KS) or the GAG linker chain, a tetrasccharide sequence required for some GAG biosyntheses to take place. Mucopolysaccharidosis IV B (MPSIVB, Morquio's syndrome B; MIM:253010) is the result of GLB1 deficiency.
GLB1 mutations causing severe phenotypes are R482C (Ishii et al. 1995), W509C (Oshima et al. 1991), Y83C (Santamaria et al. 2006) and W273L Paschke et al. 2001. Mild phenotypes where a partial loss of enzyme activity occurs can involve the mutants G438E, N484K, T500A (Bagshaw et al. 2002) and Y83H (Ishii et al. 1995). These mild phenotype mutants are not detailed here.
Literature References
PubMed ID Title Journal Year
7586649 Clinical and molecular analysis of a Japanese boy with Morquio B disease

Suzuki, Y, Ishii, N, Oshima, A, Sakuraba, H, Sukegawa, K, Matsuda, I, Orii, T, Endo, F, Oohira, T

Clin. Genet. 1995
16941474 Twenty-one novel mutations in the GLB1 gene identified in a large group of GM1-gangliosidosis and Morquio B patients: possible common origin for the prevalent p.R59H mutation among gypsies

Coll, MJ, Vilageliu, L, Chabás, A, Santamaria, R, Miranda, CS, Grinberg, D

Hum. Mutat. 2006
11511921 Mutation analyses in 17 patients with deficiency in acid beta-galactosidase: three novel point mutations and high correlation of mutation W273L with Morquio disease type B

Hoefler, G, Radeva, B, Hoeltzenbein, M, Kreimer-Erlacher, H, Paschke, E, Levade, T, Kleijer, W, Milos, I, Michelakakis, H, Beck, M

Hum. Genet. 2001
1928092 Human beta-galactosidase gene mutations in morquio B disease

Fukuhara, Y, Yoshida, K, Suzuki, Y, Sakuraba, H, Oshima, A, Shimmoto, M

Am J Hum Genet 1991
Catalyst Activity

beta-galactosidase activity of GLB1 mutants [lysosomal lumen]

Normal reaction
Functional status

Loss of function of GLB1 mutants [lysosomal lumen]

Name Identifier Synonyms
mucopolysaccharidosis DOID:12798 Mucopolysaccharidosis, Mucopolysaccharidoses, Mucopolysaccharidosis (disorder), Mucopolysaccharidosis, Mucopolysaccharidosis NOS (disorder), mucopolysaccharidosis, Mucopolysaccharidosis [Ambiguous]
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