Beta-galactosidase
- OMIM: 611 458
- UniProt: P16278
- MGI: 8815
β -galactosidases (including β - galactosidases ) are enzymes that terminal sugar residues ( galactose β ) of galactosidic degrade biomolecules (for example, gangliosides, glycoproteins and glycosaminoglycans ). They occur in all living organisms, where they have different importance in metabolism. In addition to the bacterial lactase, which is also a β -galactosidase, there are still people in a lactase, which is not expected to EC 3.2.1.23. Bacterial β -galactosidase is used in the laboratory. The human enzyme is encoded by the GLB1 gene and is found in two splice variants, which are located in all the cells, both in the lysosomes as well as in the cytoplasm. Mutations in GLB1 gene can lead to different types of gangliosidosis and mucopolysaccharidosis type 4B of.
Function
β - galactosidases catalyze the hydrolysis of the glycosidic bond of β - galactopyranosides. In an exoglycosidase here arises the monosaccharide galactose. They are different depending on the specific task and organism. So some galactosidases also α -L- Arabinopyranoside can hydrolyze.
Use
In the micro - and molecular biology is the product derived from the gram-negative bacterium Escherichia coli gene for β -galactosidase, called lacZ, used as a reporter gene. In modified by genetic engineering bacteria (eg blue - white selection of colonies), yeasts (eg, yeast two -hybrid system ) or even higher organisms (eg knockout mouse ) shows the hydrolysis of X-Gal (5- bromo-4- chloro-3- indoxyl - β -D-galactopyranoside ) to a blue to galactose and water-insoluble indigo dye, the expression of lacZ. By hydrolysis of ONPG (o- nitrophenyl- β -D-galactopyranoside ), the activity of β -galactosidase can be quantitatively determined.
Industrial β -galactosidase is used extensively in the dairy industry, for example in the production of lactose-free milk, or in the treatment of whey.
Classification
β - galactosidases form family 35 in the classification of glycosidases by Henrissat.