異丙基-β-D-硫代半乳糖苷,  Isopropyl b-D-thiogalactopyranoside

A non-metabolizable allolactose analogue, widely used in molecular biology for overexpression of recombinant proteins from inducible systems under the control of lac promoter. IPTG binds to the LacI repressor and causes its release from the lac operator, allowing gene expression to take place. Present in vectors of pGEX, pGEM-T, pET, pRSET, pMAL class and others.

What is IPTG?

IPTG is a chemical akin to galactose. It is unable to be hydrolyzed by the enzyme ss-Galactosidase.

IPTG is a galactose analog, which is not metabolizable and inhibits the lac repressor

IPTG is an atomic replica of allolactose, a lactose metabolite that triggers the transcription that activates the operon. It is utilized with a concentration between 100 mM and 1.5 mM to stimulate protein expression when this gene operates under the control of the lac operator. It can be used in conjunction with X-gal and bluo-gal to determine the activity of the lac gene during cloning processes.

IPTG is an S-glycosyl compound consisting of beta-D-1-thiogalactose having an isopropyl group attached to the anomeric sulfur.

Location of IPTG

In the vectors of pGEX, PGEM-T, PET, pRSET, the PMA class, and many more.

Biochemical Activity of IPTG

IPTG can be an option to be used with X-GAL when cloning techniques require the expression of b-galactosidase. An analog that is not metabolizable of galactose.

Allosteric lac inhibits protein repressors. Induces b-galactosidase (LacZ) expression. It is used in conjunction with X-gal to select the blue/white of recombinant bacteria.

Mechanism of action of IPTG

Similar to allolactose, IPTG bonds with the lac repressor and removes the tetrameric repressor, the operator of lac, in an allosteric way that allows for to regulate genes that are part of the lac operon like the beta-galactosidase gene, which is a hydrolase enzyme that is responsible for the hydrolysis of b-galactosides to monosaccharides.

However, unlike allolactose, the sulfur (S) atom forms a chemical bond that cannot be hydrolyzed by the cell, preventing the cell from degrading or metabolizing the stimulant. Thus, its concentration stays constant throughout the study.

IPTG intake via E. coli can be independent of the activity of lactose permease since other transport pathways are involved. 1. At low levels, IPTG enters cells through lactose permease. But at higher concentrations (typically used to induce protein), IPTG can enter the cells in a way that is not dependent on lactose permease.

Uses of IPTG

IPTG is often used in cloning techniques that induce B-galactosidase activity. It is employed alongside X-Gal or Bluo-Gal for blue-white selection of colony recombinant bacterial strains that cause lac operon expression within Escherichia coli. IPTG is a protein that binds to the lac-repressor altering its structure that prevents the inhibition of the b-galactosidase-coding gene lacZ.

The lac operon is a critical factor in the regulation of the expression of the protein.

Genes controlled by lac or tac promotor/operator/sequences are expressed at high levels in the presence of IPTG.

IPTG is also employed in the induction of recombinant protein. In these systems, a protein of significance is encoded downstream from IPTG's IPTG inducer. The cell culture is then divided, and the protein is extracted and purified using various methods, such as the His Tag and GST removal systems (for proteins with tags for ligands).

Title: IPTG

CAS Registry Number: 367-93-1

CAS Name: 1-Methylethyl 1-thio-b-D-galactopyranoside

Additional Names: isopropyl b-D-thiogalactopyranoside

Molecular Formula: C9H18O5S

Molecular Weight: 238.30

Percent Composition: C 45.36%, H 7.61%, O 33.57%, S 13.46%

Literature References: Artificial, slow-hydrolyzing inducer of the lactose (lac) operon. Prepn: B. Helferich, D. Türk, Ber. 89, 2215 (1956); U. Carlsson et al., Protein Eng. 4, 1019 (1991). Induction of b-galactosidase: V. Paces et al., Collect. Czech. Chem. Commun. 38, 2983 (1973). Binding to b-D-galactosidase: C. K. De Bruyne, M. Yde, Carbohydr. Res. 56, 153 (1977). Concentration effects on lac operon induction in E. coli: S. Cho et al., Biochem. Biophys. Res. Commun. 128, 1268 (1985). Effect of lactose permease on induction by IPTG: L. H. Hansen et al., Curr. Microbiol. 36, 341 (1998).

Properties: mp 109.5-110.5°. [a]D22 -31.4° (c = 5 in water). Also reported as crystals from dioxane, mp 118-119°. [a]D -26.4° (c = 1 in water) (Carlsson). Log P (octanol/water): -1.26.

Melting point: mp 109.5-110.5°; mp 118-119°

Optical Rotation: [a]D22 -31.4° (c = 5 in water); [a]D -26.4° (c = 1 in water) (Carlsson)

Log P: Log P (octanol/water): -1.26

Use: Induces protein synthesis in E. coli when transcription is controlled by the lac-promoter. In conjunction with X-gal, q.v., in detection of lac gene activity during cloning experiments.

1. The raw material, D-galactose, is from plant.
2. Our product is free of dioxane.
3. The scale can be up to ton.
4. The purity is min.99% by TLC and min.98% by HPLC.
5. No unpleasant ordor can be smelt.

References:

1. Lama J, et al., Gene 1992, 117, 185
2. Zhang Y, Moss B, Natl. Acad. Sci. USA, 1991, 88, 1511
3. Rodriquez JF, Smith GL, Nucleic Acids Res. 1990, 18, 5347
4. Date T, et al., Biochem. Biophys. Res. Commun. 1988, 151, 598
5. Lee SG, et al., Biochemistry 1988, 27, 2983