β-Galactosidase powder

β -Galactosidase More Info

Function

β -Galactosidase is an exoglycosidase which hydrolyzes the β-glycosidic bond formed between a galactose and its organic moiety. It may also cleave fucosides and arabinosides but at a much lower rate. It is an essential enzyme in the human body. Deficiencies in the protein can result in galactosialidosis or Morquio B syndrome. In E. coli, the lacZ gene is the structural gene for β-galactosidase; which is present as part of the inducible system lac operon which is activated in the presence of lactose when glucose level is low. β-Galactosidase synthesis stops when glucose levels are sufficient.

β -Galactosidase has many homologues based on similar sequences. A few are evolved β-galactosidase (EBG), β-glucosidase, 6-phospho-β-galactosidase, β-mannosidase, and lactase-phlorizin hydrolase. Although they may be structurally similar, they all have different functions. Beta-gal is inhibited by L-ribose and by competitive inhibitors 2-phenylethyl 1-thio-β-D-galactopyranoside (PETG), D-galactonolactone, isopropyl thio-β-D-galactoside (IPTG), and galactose.

β -Galactosidase is important for organisms as it is a key provider in the production of energy and a source of carbons through the break down of lactose to galactose and glucose. It is also important for lactose-intolerant people as it is responsible for making lactose-free milk and other dairy products. Many adult humans lack the lactase enzyme, which has the same function as β-galactosidase, so they are not able to properly digest dairy products. β-Galactose is used in such dairy products as yogurt, sour cream, and some cheeses which are treated with the enzyme to break down any lactose before human consumption. In recent years, β-galactosidase has been researched as a potential treatment for lactose intolerance through gene replacement therapy where it could be placed into the human DNA so individuals can break down lactose on their own.

Structure

The 1,023 amino acids of E. coli β-galactosidase were sequenced in 1983, and its structure determined eleven years later in 1994. The protein is a 464-kDa homotetramer with 2,2,2-point symmetry. Each unit of β-galactosidase consists of five domains; domain 1 is a jelly-roll type β-barrel, domain 2 and 4 are fibronectin type III-like barrels, domain 5 a novel β-sandwich, while the central domain 3 is a distorted TIM-type barrel, lacking the fifth helix with a distortion in the sixth strand.