4-Nitrophenyl beta-D-galactopyranoside CAS:200422-18-0

Effect: ONPG is a substrate specifically used to detect the presence and activity of the enzyme β-galactosidase. When β-galactosidase enzyme is present and active, it cleaves ONPG into two products: o-nitrophenol and a galactose derivative. The liberation of o-nitrophenol results in a yellow color change, which can be measured using a spectrophotometer.

Application: ONPG has several applications in molecular biology and biochemistry research:

Determination of β-galactosidase activity: ONPG is commonly used to measure and quantify the activity of β-galactosidase enzyme. The rate of o-nitrophenol formation, which is directly proportional to the enzyme activity, can be measured spectrophotometrically.

Gene expression and regulation: ONPG is often utilized in experiments related to gene expression and regulation studies. It is frequently used in fusion protein assays, such as the commonly used lacZ fusion system, to study the expression of genes under the control of specific promoters. The beta-galactosidase activity measured using ONPG provides insights into the level of gene expression.

Screening for β-galactosidase activity: ONPG can be used as a colorimetric screening method in recombinant DNA technology to identify the presence and functionality of the LacZ gene, which encodes β-galactosidase. This screening method helps in identifying clones that contain the gene of interest.

Enzyme kinetics studies: ONPG is also useful in studying the kinetics of β-galactosidase enzyme. By measuring the rate of enzyme-substrate reaction at different substrate concentrations, it is possible to determine kinetic parameters such as Michaelis-Menten constants (Km) and maximum reaction rates (Vmax).