X-gal: Difference between revisions

X-gal is an [[Structural analog|analog]] of [[lactose]], and therefore may be hydrolyzed by the [[beta-galactosidase|β-galactosidase]] enzyme which cleaves the β-[[glycosidic bond]] in D-lactose. X-gal, when cleaved by β-galactosidase, yields galactose and 5-bromo-4-chloro-3-hydroxyindole. The latter then spontaneously dimerizes and is oxidized into 5,5'-dibromo-4,4'-dichloro-[[Indigo_dye|indigo]], an intensely blue product which is insoluble. X-gal itself is colorless, so the presence of blue-colored product therefore may therefore be used as a test for the presence of an active β-galactosidase. This easy identification of an active enzyme allows the gene for β-galactosidase (the ''lacZ ''gene) to be used as a [[reporter gene]] in various applications.<ref>{{cite book|title=Recombinant DNA Technology |first=Sardul Singh |last=Sandhu |year=2010 |publisher=I K International Publishing House |isbn=978-9380578446 |page=116}}</ref>