Which Of The Following Is A Structural Analogue For Lactose Used In The Lab Gene Expression Experiments And Does Not Induce The Enzyme But Functions As A Substrate For The Enzyme? (2023)

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Which Of The Following Is A Structural Analogue For Lactose Used In The Lab Gene Expression Experiments And Does Not Induce The Enzyme But Functions As A Substrate For The Enzyme? ›

The structural analogue for lactose that is used in gene expression experiments and does not induce the enzyme but functions as a substrate for the enzyme is ONPG

IPTG is easily transported into normal E. coli cells where it binds and inhibits the action of the LacI repressor protein and effectively activates lac operon expression. Unlike lactose though, IPTG cannot be cleaved by ß-galactosidase and remains within the cell as a constant activator of lac operon expression.

i) Lactose is the substrate for the enzyme β-galactosidase and regulates switching on and off of the operon.

z-gene codes for β-galactosidase (β-gal) which is responsible for the hydrolysis of the disaccharide lactose into its monomeric units galactose and glucose.

☰ The ONPG test is used to detect the enzyme β-galactosidase , present in late lactose fermenters (late lactose fermenters are very difficult to distinguish from non-lactose fermenters because both appear under form colorless colonies on MacConkey agar ).

Why is IPTG Better than Lactose for Induction? The bacterial cells can't process IPTG since it is not the right substrate for the lactose metabolic pathways. Therefore, IPTG remains available in the growth medium for inducing protein expression, instead of being used up as an energy source.

The BL21(DE3) strain is widely used for recombinant protein production because of its engineered capacity to produce T7 polymerase and its deficiency in Lon and OmpT proteases.

The LCT gene provides instructions for making an enzyme called lactase. This enzyme helps to digest lactose, a sugar found in milk and several other dairy products. Lactase is produced by some of the cells that line the walls of the small intestine.

The lactose synthesis reaction is catalyzed by lactose synthase (UDP-galactose : D-glucose l-galactosyl transferase, EC 2.4. 1.22), a complex of β-1, 4-galactosyltransferase (β4GalT-I) and the essential cofactor α-lactalbumin (α-LA), in the Golgi compartment [6, 7].

Lactase is an enzyme that helps your body digest lactose. You'll find lactose in dairy foods like milk and cheese. The lactase supplement prevents bloating, diarrhea and gas caused by lactose intolerance.

What is the name of the enzymes responsible for hydrolyzing proteins into amino acids? ›

Proteolytic enzymes (also termed peptidases, proteases and proteinases) are capable of hydrolyzing peptide bonds in proteins.

As an enzyme, β-galactosidase cleaves the disaccharide lactose to produce galactose and glucose which then ultimately enter glycolysis.

Final answer: Lactobacillus converts lactose (milk sugar) into lactic acid and helps in the formation of lactic acid.

What is the purpose of ONPG in this lab? Acts as a substrate that gives a yellow color when cleaved. What is the purpose of sodium carbonate (Na2CO3) in this lab? To drastically change the pH and stop the enzymatic reaction between beta-galactosidase and ONPG.

ONPG test is a very sensitive test for lactose-fermentation. In this test, O-Nitrophenyl-β-D-galactopyranoside (ONPG) (artificial in nature) acts as a substrate for beta-galactosidase to ascertain the specific enzyme activity that serves in the identification and differentiation of organisms.

Note: “ONPG” (also known as “2-Nitrophenyl β-D-galactopyranoside”) is a Chemical analog of the sugar lactose and is hydrolysed by the enzyme lactase. Like β- galactosidase, lactase breaks lactose down into galactose and glucose. The test should be performed, where possible, from a non-selective medium.

IPTG will bind to lac repressors and liberate tetrameric repressors from the lac operator. This will allow for the transcription genes in the lac operon to catalyze the hydrolysis of ß-galactosidase into monosaccharides.

IPTG is a structural mimic of lactose (it resembles the galactose sugar) that also binds to the lac repressor and induces a similar conformational change that greatly reduces its affinity for DNA. Unlike lactose, IPTG is not part of any metabolic pathways and so will not be broken down or used by the cell.

IPTG (isopropyl beta-D-thiogalactoside) Inducer for Beta-Galactosidase Expression acts as a molecular mimic of a lactose metabolite. The presence of IPTG triggers the activation of the lac operon for downstream gene transcription due to its binding the lac repressor.

This has been demonstrated by growing Escherichia coli on glycerol in the presence of Isopropyl-β-D-1-thiogalactopyranoside (IPTG) to induce β-galactosidase synthesis which does not offer any benefit towards growth.