Function
α-Galactosidase (Agal) hydrolyzes the terminal α-galactosyl moiety from glycoproteins and glycolipids[1].
- β-Galactosidase (Bgal) hydrolyzes β-galactosides into monosaccharides[2].
Isopropyl-β-d-thiogalactopyranoside (IPTG) induces Bgal activity. Phenylethyl-β-d-thiogalactopyranoside (PETG) is an inhibitor. Galactose, lactose, o-nitrophenyl-β-d-galactoside (ONPG) are substrates. Galactopyranosyl is reaction intermediate.
For details on α-galactosidase see Garman lab: Interconversion of lysosomal enzyme specificities.
For details on β-galactosidase see Molecular Playground/Beta-galactosidase.
See also: Beta-galactosidase (hebrew)
- Endo-1,4-β-galactosidase hydrolyzes pectic galactans to produce D-galactose, beta-1,4-D galactobiose, beta-1,4-D galactotriose and beta-1,4-D galactotetraose[3].
See also Lactase (a protein)
Relevance
Bgal assay is used in molecular biology to monitor gene expression.
Disease
The inherited deficiency of Agal is the cause of Fabry disease[4]. Bgal mutations causing enzyme deficiency can lead to ganglioidosis[5].
Structural highlights
The Zn+2 binding site is composed of 4 Cys residues. The galactose binding site is seen in a large central channel[6]. Water molecules shown as red spheres.
For 3hg2 click here to see cycling morph from empty active site to substrate bound form and back.
3D Structures of Galactosidase
Galactosidase 3D structures
- ↑ Garman SC, Garboczi DN. The molecular defect leading to Fabry disease: structure of human alpha-galactosidase. J Mol Biol. 2004 Mar 19;337(2):319-35. PMID:15003450 doi:10.1016/j.jmb.2004.01.035
- ↑ Jacobson RH, Zhang XJ, DuBose RF, Matthews BW. Three-dimensional structure of beta-galactosidase from E. coli. Nature. 1994 Jun 30;369(6483):761-6. PMID:8008071 doi:https://dx.doi.org/10.1038/369761a08015589
- ↑ Yang H, Ichinose H, Yoshida M, Nakajima M, Kobayashi H, Kaneko S. Characterization of a thermostable endo-beta-1,4-D-galactanase from the hyperthermophile Thermotoga maritima. Biosci Biotechnol Biochem. 2006 Feb;70(2):538-41. PMID:16495677 doi:10.1271/bbb.70.538
- ↑ Kint JA. Fabry's disease: alpha-galactosidase deficiency. Science. 1970 Feb 27;167(3922):1268-9. PMID:5411915
- ↑ Morrone A, Bardelli T, Donati MA, Giorgi M, Di Rocco M, Gatti R, Parini R, Ricci R, Taddeucci G, D'Azzo A, Zammarchi E. beta-galactosidase gene mutations affecting the lysosomal enzyme and the elastin-binding protein in GM1-gangliosidosis patients with cardiac involvement. Hum Mutat. 2000;15(4):354-66. PMID:10737981 doi:<354::AID-HUMU8>3.0.CO;2-L 10.1002/(SICI)1098-1004(200004)15:4<354::AID-HUMU8>3.0.CO;2-L
- ↑ Hidaka M, Fushinobu S, Ohtsu N, Motoshima H, Matsuzawa H, Shoun H, Wakagi T. Trimeric crystal structure of the glycoside hydrolase family 42 beta-galactosidase from Thermus thermophilus A4 and the structure of its complex with galactose. J Mol Biol. 2002 Sep 6;322(1):79-91. PMID:12215416
