Galactosidase is an enzyme that breaks down some types of sugar into sugars that biological organisms can use for energy, such as glucose. Galactosidase has to sub-groups, alpha and beta.
Alpha-galactosidase can break down compounds which contain alpha-galactosidic residues, including glycoproteins and glycosphingolipids.
Beta-galactosidase is the enzyme that our bodies need to break down the sugar in milk, lactose, into forms that our bodies can process, such as glucose and galactose.
Recently, a new form of beta-galactosidase has been found that is created by a cold-adapted bacteria that live in the Antarctic. This bacteria produces a type of beta-galactosidase which functions of temperatures of around 4 degrees celsius. The enzyme does its work at low temperature, avoiding spoilage and keeping waste down.
Beta-galactosidase is made up of four identical subunits - all polypeptide chains. The interesting thing about the molecule is that you can separate in half and then stitch it back together again and it will regain its enzymatic functions. The inactive fragments will suddenly become active again, opening up a range of applications which require the ability to turn the enzyme on and off.
One of the benefits of the structural properties of galactosidase is that it allows researchers to track the efficiency of bacterial transformation.
The the bacteria contains a recombinant plasmid, a structure which contains genetic information outside of the DNA. When galactosidase is split into two parts, it becomes encoded by different parts of the gene in a process called alpha-complementation.
The lac operon encodes the "omega" fragment in the bacteria’s chromosome, and the genes found in the plasmid encodes the alpha fragment.
The fragments are not produced when the genes are not present. This fact allows researchers to track whether specific genes are present in the bacteria. If both genes in the chromosome and the plasmid are not present, the omega and alpha fragments cannot come together to produce beta-galactosidase. Researchers can, therefore, test for the presence of beta-galactosidase and then determine whether genes are present or not.
galactosidase can be detected through the hydrolysis of X-gal by galactosidase in the bacteria. The hydrolysis of this compound by the enzyme products a blue-coloured compound. If galactosidase is not present, it creates a white compound, if on the addition of X-gal to the colony it turns blue, the target genes are present in both the plasmid and chromosome.