GLB1

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Galactosidase, beta 1
Available structures
PDB Ortholog search: PDBe, RCSB
Identifiers
Symbols GLB1 ; EBP; ELNR1; MPS4B
External IDs OMIM611458 MGI88151 HomoloGene47922 ChEMBL: 2522 GeneCards: GLB1 Gene
EC number 3.2.1.23
RNA expression pattern
PBB GE GLB1 201576 s at tn.png
More reference expression data
Orthologs
Species Human Mouse
Entrez 2720 12091
Ensembl ENSG00000170266 ENSMUSG00000045594
UniProt P16278 P23780
RefSeq (mRNA) NM_000404 NM_009752
RefSeq (protein) NP_000395 NP_033882
Location (UCSC) Chr 3:
33.04 – 33.14 Mb
Chr 9:
114.4 – 114.47 Mb
PubMed search [1] [2]

Galactosidase, beta 1, also known as GLB1, is a protein which in humans is encoded by the GLB1 gene.[1][2]

The GLB1 protein is a beta-galactosidase that cleaves the terminal beta-galactose from ganglioside substrates and other glycoconjugates.[3] The GLB1 gene also encodes an elastin binding protein.[4]

In corn (Zea mays), Glb1 is a gene coding for the storage protein globulin.

Clinical significance[edit]

GM1-gangliosidosis is a lysosomal storage disease that can be caused by a deficiency of β-galactosidase (GLB1). Some cases of Morquio syndrome B have been shown to be due to GLP1 mutations that cause patients to have abnormal elastic fibers.[5]

Elastin receptor[edit]

The RNA transcript of the GLB1 gene is alternatively spliced and produces 2 mRNAs. The 2.5-kilobase transcript encodes the beta-galactosidase enzyme of 677 amino acids. The alternative 2.0-kb mRNA encodes a beta-galactosidase-related protein (S-Gal) that is only 546 amino acids long and that has no enzymatic activity. The S-Gal protein does bind elastin and fragments of elastin that are generated by proteolysis.[6]

The S-Gal protein is a peripheral membrane protein that functions as part of an elastin receptor complex on the surface of cells.[7] The elastin receptor complex includes S-Gal, neuraminidase and Cathepsin A. When elastin-derived peptides bind to the S-Gal protein then the associated neuraminidase enzyme activity is activated and responding cells can have altered signal transduction involving extracellular signal-regulated kinases and regulated matrix metallopeptidase production. Elastin-derived peptides are chemotactic for some cell types[8] and can alter cell cycle progression.[9] The ability of the GLB1-derived elastin binding protein and the elastin receptor complex to influence cell proliferation appears to be indirect and involve removal of sialic acid from extracellular and cell surface proteins such as growth factor receptors.

The S-Gal protein functions during the normal assembly of elastin into extracellular elastic fibers. Elastin is initially present as newly synthesized tropoelastin which can be found in association with S-Gal. The enzymatic activity of neuraminidase in the elastin receptor complex is involved in the release of tropoelastin molecules from the S-Gal chaperone.[10] Cathepsin A is also required for normal elastin biosynthesis.[11]

References[edit]

  1. ^ Shows TB, Scrafford-Wolff L, Brown JA, Meisler M (1978). "Assignment of a beta-galactosidase gene (beta GALA) to chromosome 3 in man". Cytogenet. Cell Genet. 22 (1-6): 219–22. doi:10.1159/000130940. PMID 110522. 
  2. ^ Oshima A, Tsuji A, Nagao Y, Sakuraba H, Suzuki Y (November 1988). "Cloning, sequencing, and expression of cDNA for human beta-galactosidase". Biochem. Biophys. Res. Commun. 157 (1): 238–44. doi:10.1016/S0006-291X(88)80038-X. PMID 3143362. 
  3. ^ Yoshida K, Oshima A, Shimmoto M, Fukuhara Y, Sakuraba H, Yanagisawa N, Suzuki Y (August 1991). "Human beta-galactosidase gene mutations in GM1-gangliosidosis: a common mutation among Japanese adult/chronic cases". Am. J. Hum. Genet. 49 (2): 435–42. PMC 1683306. PMID 1907800. 
  4. ^ Caciotti A, Donati MA, Boneh A, et al. (March 2005). "Role of beta-galactosidase and elastin binding protein in lysosomal and nonlysosomal complexes of patients with GM1-gangliosidosis". Hum. Mutat. 25 (3): 285–92. doi:10.1002/humu.20147. PMID 15714521. 
  5. ^ Hinek A, Zhang S, Smith AC, Callahan JW (July 2000). "Impaired elastic-fiber assembly by fibroblasts from patients with either Morquio B disease or infantile GM1-gangliosidosis is linked to deficiency in the 67-kD spliced variant of beta-galactosidase". Am J Hum Genet. 67 (1): 23–36. doi:10.1086/302968. PMC 1287082. PMID 10841810. 
  6. ^ Privitera S, Prody CA, Callahan JW, Hinek A (March 1998). "The 67-kDa enzymatically inactive alternatively spliced variant of beta-galactosidase is identical to the elastin/laminin-binding protein". J Biol Chem. 273 (11): 6319–6326. doi:10.1074/jbc.273.11.6319. PMID 9497360. 
  7. ^ Duca L, Blanchevoye C, Cantarelli B, Ghoneim C, Dedieu S, Delacoux F, Hornebeck W, Hinek A, Martiny L, Debelle L (February 2007). "The elastin receptor complex transduces signals through the catalytic activity of its Neu-1 subunit". J Biol Chem. 282 (17): 12484–12491. doi:10.1074/jbc.M609505200. PMID 17327233. 
  8. ^ Adair-Kirk TL, Senior RM (December 2008). "Fragments of Extracellular Matrix as Mediators of Inflammation". Int J Biochem Cell Biol. 2008;40(6-7): 40 (6-7): 1101–1110. doi:10.1016/j.biocel.2007.12.005. PMC 2478752. PMID 18243041. 
  9. ^ Hinek A, Bodnaruk TD, Bunda S, Wang Y, Liu K (October 2008). "Neuraminidase-1, a subunit of the cell surface elastin receptor, desialylates and functionally inactivates adjacent receptors interacting with the mitogenic growth factors PDGF-BB and IGF-2". Am J Pathol. 173 (4): 1042–1056. doi:10.2353/ajpath.2008.071081. PMC 2543072. PMID 18772331. 
  10. ^ Hinek A, Pshezhetsky AV, von Itzstein M, Starcher B (February 2006). "Lysosomal sialidase (neuraminidase-1) is targeted to the cell surface in a multiprotein complex that facilitates elastic fiber assembly". J Biol Chem. 281 (6): 3698–3710. doi:10.1074/jbc.M508736200. PMID 16314420. 
  11. ^ Seyrantepe V, Hinek A, Peng J, Fedjaev M, Ernest S, Kadota Y, Canuel M, Itoh K, Morales CR, Lavoie J, Tremblay J, Pshezhetsky AV (April 2008). "Enzymatic activity of lysosomal carboxypeptidase (cathepsin) A is required for proper elastic fiber formation and inactivation of endothelin-1". Circulation 117 (15): 1973–1981. doi:10.1161/CIRCULATIONAHA.107.733212. PMID 18391110. 

Further reading[edit]