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)

1. [PDF] Effect Of Lactose On The ONPG ?-Galactosidase Assay

  • In the following experiment, we have used the lactose analogue isopropyl thiogalactoside (IPTG) to induce lac operon expression in E. coli to high levels ...

2. LacZ β-galactosidase: Structure and function of an enzyme of historical ...

  • Sep 25, 2012 · Lactose is probably the natural substrate of β-galactosidase,30 but the enzyme is promiscuous for the nongalactose part of the substrate. Many ...

  • This review provides an overview of the structure, function, and catalytic mechanism of lacZ β-galactosidase. The protein played a central role in Jacob and Monod's development of the operon model for the regulation of gene expression. Determination ...

LacZ β-galactosidase: Structure and function of an enzyme of historical ...

3. Structural Explanation for Allolactose (lac Operon Inducer) Synthesis by ...

Structural Explanation for Allolactose (lac Operon Inducer) Synthesis by ...

4. [PDF] The Genetics of Beta-galactosidase- Encoded by the lacZ gene in E. coli

  • ... structural analog of lactose, is a more potent inducer than lactose. Unlike lactose, IPTG is not hydrolyzed by the induced enzyme. This experiment will ...


6. The lac operon (article) | Khan Academy

  • The lac repressor senses lactose indirectly, through its isomer allolactose. Catabolite activator protein (CAP) acts as a glucose sensor. It activates ...

  • Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

The lac operon (article) | Khan Academy

7. [PDF] Lac Operon Expression in Steady State Cells of Escherichia coli

  • containing non-metabolizable lactose structural analogs. (e.g.: IPTG or TMG? ... although the induced BG was different in structure and enzyme activity from ...

8. [PDF] Structural characterization of the β-galactosidase from ... - UDC

  • Parte del capítulo 4 de esta tesis ha sido realizado en el Departamento de Engenharia. Biológica da Universidade do Minho (Braga, Portugal) durante una estancia ...

9. Chapter 6: Enzyme Principles and Biotechnological Applications

  • These RNAs, which are called ribozymes, play an important role in gene expression. ... not physically block the substrate binding site, but it does prevent ...

  • Chapter 6: Enzyme Principles and Biotechnological Applications 6.1 The Nature and Classification of Enzymes 6.2 Enzyme Names and Classification 6.3 Enzyme Structure and Substrate Binding 6.4 Enzymes and Reaction Equilibrium 6.5 Properties and Mechanisms of Enzyme Action 6.6 Enzymes are Affected by pH and Temperature 6.7 Enzymes are Sensitive to Inhibitors 6.8 Allosteric Regulators and […]

Chapter 6: Enzyme Principles and Biotechnological Applications


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

ortho-Nitrophenyl-β-galactoside (ONPG) is a colorimetric and spectrophotometric substrate for detection of β-galactosidase activity. This compound is normally colorless. However, if β-galactosidase is present, it hydrolyzes the ONPG molecule into galactose and ortho-nitrophenol.
https://en.wikipedia.org › Ortho-Nitrophenyl-β-galactoside

Why is IPTG rather than lactose used to induce β-galactosidase synthesis in the experimental system in this lab? ›

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.

Is lactose the substrate for the enzyme? ›

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

Which gene codes for an enzyme which is responsible for hydrolysis of lactose? ›

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.

What is ONPG used for? ›

☰ 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 IPTG is used instead of lactose? ›

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.

Why BL21 is used for protein expression? ›

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.

What enzymes are responsible for lactose? ›

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.

What are the enzymes for lactose synthesis? ›

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].

What is the enzyme for lactose? ›

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.

What is the enzyme that is responsible for converting lactose to galactose called? ›

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

Which enzyme converts lactose to lactic acid? ›

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 quizlet? ›

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.

What is the ONPG test for lactose? ›

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.

What is the enzyme in the ONPG test? ›

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.

What does IPTG do to beta galactosidase? ›

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.

How is IPTG different from lactose structure? ›

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.

How does IPTG affect beta galactosidase expression? ›

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.

Does IPTG induce beta galactosidase? ›

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.


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