It is sometimes loosely referred to as lactase but that name is generally reserved for mammalian digestive enzymes that breaks down lactose specifically.)

[3] 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.

[4] 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.

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.

[citation needed] These structural features provide a rationale for the phenomenon of α-complementation, where the deletion of the amino-terminal segment results in the formation of an inactive dimer.

In one, it can go through a process called transgalactosylation to make allolactose, creating a positive feedback loop for the production of β-galactose.

Galactosylation is the first chemical step in the reaction where Glu461 donates a proton to a glycosidic oxygen, resulting in galactose covalently bonding with Glu537.

In the second step, degalactosylation, the covalent bond is broken when Glu461 accepts a proton, replacing the galactose with water.

When water participates in the reaction, galactose is formed, otherwise, when D-glucose acts as the acceptor in the second step, transgalactosylation occurs .

The β-linkage of the substrate is cleaved by a terminal carboxyl group on the side chain of a glutamic acid.

β-galactosidase will cleave the glycosidic bond in X-gal and form galactose and 5-bromo-4-chloro-3-hydroxyindole which dimerizes and oxidizes to 5,5'-dibromo-4,4'-dichloro-indigo, an intense blue product that is easy to identify and quantify.

However, when DNA fragments are inserted in the vector, the production of LacZα is disrupted, the cells therefore show no β-galactosidase activity.

In studies of leukaemia chromosomal translocations, Dobson and colleagues used a fusion protein of LacZ in mice,[17] exploiting β-galactosidase's tendency to oligomerise to suggest a potential role for oligomericity in MLL fusion protein function.

Beta-Galactosidase activity can be overexpressed, and this can lead to various diseases afflicting a wide range of body systems.

Two classes of single point mutations dramatically improve the activity of ebg enzyme toward lactose.

[32] A study targeted at identifying fruit softening of peaches found 17 different gene expressions of β-galactosidases.