Questions tagged [enzymes]

Enzymes are globular proteins that catalyse a biochemical reaction, increasing the overall rate by reducing activation energy. Most chemical reactions in a cell need enzymes in order to occur at rates sufficient to sustain life.

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807 views

Rate-determining steps in enzyme catalysed reactions

According to my chemistry book, there are 3 simplified steps within an enzyme catalysed reaction: S + E → ES ES → EP EP → E + P Where S is substrate, E is enzyme, ES is enzyme substrate complex, EP ...
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In the Lineweaver-Burk Plot, why does the x-intercept = -1/Km?

Taking the reciprocal of both sides of the Michaelis-Menten equation yields the Lineweaver-Burk Equation: $ \dfrac{1}{V} = \dfrac{K_m}{V_{max}}\dfrac{1}{[S]}+ \dfrac{1}{V_{max}} $ Plotting a $ \...
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Does protein kinase A accelerate glycolysis or slow it down?

In liver cells, the activity of PFK-1 is regulated by the PFK-2/FBP-2 complex, whose activity is in turn controlled by glucagon and insulin. Glucagon activates protein kinase A. Then protein kinase ...
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How does changing the shape of ATP synthase specifically prevent the enzyme from working any longer?

I am currently stuck on working out how to answer this question: "A random mutation causes the enzyme ATP synthase to change shape so that it can no longer function. Describe the impact this would ...
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Does DNA helicase or topoisomerase actually “unwind” DNA?

I am reading through my textbook (Genetics, Brooker 4th edition) and the summary it gives seems imprecise for the functionality of helicase and topoisomerase. The following is an exerpt: ...
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Understanding of the saturation function in the Monod-Wyman-Changeux Model

I am reading Mathematical Physiology, Sneyd. I am a undergraduate mathematician interested in pursuing the field, so forgive me if my terminology is off. In this example, the writer considers a ...
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Enzyme inhibitors, reversible or irreversible? [closed]

So far, I know about competitive, non-competitive inhibitors and allosteric inhibitor. Which ones are reversible and which ones are irreversible?
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Enzyme Inhibition by alpha-2 macroglobulin

Alpha-2 macroglobulin is a plasma protein which acts as an anti-protease. It does so by a "bait mechanism" - the protease cleaves the bait domain, following which a conformational change causes ...
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Can dissolved aluminium from centrifuge tank deactivate enzymes?

I extract an enzyme called diamine oxidase with a tubular centrifuge. The centrifuge uses an aluminium tank to collect the liquide after centrifugation. I asked myself what would happen if some ...
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Where do I purchase this Trypsin?

I am currently on the lookout for Trypsin, but I have some trouble finding something that is fairly cheap, ships to Europe and is equivalent to this Trypsin: http://www.emsdiasum.com/microscopy/...
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Origin of enzyme names

Sometimes I get confused about why this or that enzyme was named in this or that particular way. 1) TCA: Why was not isocitrate dehydrogenase named isocitrate decarboxylase? Wouldn't it have been at ...
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How can you stabilize enzymes in pellets made from microcrystalline cellulose?

I want to make pellets consisting of mainly the following: microcrystalline cellulose saccharose rice starch ascorbic acid glycerin and an enzyme as active component. Is it furthermore necessary to ...
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How do poikilotherms thrive in a wide range of core temperatures? [closed]

What is it about the metabolism of a poikilotherm that enables them to adapt to the surrounding temperature?
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Kinases that are ATP-sensitive at physiological conditions?

Phosphorylation is an ATP-dependent process performed by kinases. At physiological conditions it is generally assumed that ATP concentration is high enough so that ATP is not a limiting factor. ...
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Optimum pH of Catalase

I am aware that certain organs in the body have specific pH environments to increase the activity of their enzymes. I'm also aware that enzymes only work at certain pHs due to the configuration of the ...
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Catalytic Triad of Serine Proteases

Is serine considered an acid in the catalytic triad involved in the mechanism of action of serine proteases? It is donating a proton to His but I am not sure if this really qualifies as an acid?
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Enzyme Activity under High Pressure

Wikipedia has this image titled "Pressure Chamber to measure Enzyme Activity under High Pressure" Made me wonder why do we need to measure Enzyme Activity under high pressure? Are there enzymes in ...
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Are there known functions of AST, ALT, and amylase in the blood?

A number of enzymes can be measured in the blood or plasma that aid in the diagnosis of certain diseases. For example, patients with particular liver diseases may have elevated aspartate ...
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How are constitutive enzymes regulated?

I found that inducible enzymes can be regulated by many ways, but I cannot find how constitutive enzymes are regulated...
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Why does uncompetitive inhibition decrease the Michaelis constant?

I can't seem to find a good resource online that clearly outlines the difference between an uncompetitive, noncompetitive, and mixed inhibitor (I understand competitive inhibitor though). More ...
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Why is the formation of an enzyme-substrate complex endergonic (induced fit model)?

In the section about the induced fit model for enzyme substrate binding, my MCAT textbook claims that "The substrate has induced a change in the shape of the enzyme. This interaction requires energy, ...
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Do disaccharidases require a cofactor or coenzyme to function?

I'm doing research on lactose intolerance and am curious if disaccharidases (enzymes that break down disaccharides) require a cofactor or coenzyme to function? Reviews or references would be greatly ...
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How does imatinib recognize the constitutively active Abl-BCR even though it binds to the inactive conformation?

In chronic myelogenous leukemia (CML) ABL-BCR is constitutively active (always on) and it can be inhibited by imatinib and dasatinib. A study says that imatinib binds to the inactivated state of the (...
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Enzymes and Reversibility of Reactions

Richard Feynman mentions in the third chapter of The Feynman Lectures: So the real system is in the GDP-GTP transformation; in the dark the GTP which has been stored up during the day is used to ...
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What can saliva tell about ones health? [closed]

I was wondering if I d want to analyze something related to my current health based on my saliva. What could it be? I mean e.g. by putting a thermometer in your mouth you can know your body ...
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EC number classification of synthase?

It is quoted in wikipedia that: Following the EC number classification, they belong to the group of ligases , with lyases catalysing the reverse reaction. And we all know that enzymes are ...
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Why is aconitase classified as a lyase?

Aconitase in the TCA (tricarboxylic acid) cycle isomerizes citric acid to isocitric acid via cis-aconitic acid intermediate. Since overall it functions as an isomerase, why it does not belong to ...
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Relative concentration of enzyme vs reaction product

I was reading a paper in which a recombinant protein (His-6 tagged) is expressed in E Coli (BL21 DE3). The yield of the enzyme isolated from the culture is reported as 10-30 mg per L of bacterial ...
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Can ELISA be used to detect a plant enzyme? Creating assay for a new enzyme

If the goal is to generate a rapid assay for an enzyme of plant source what are the typical options? i.e. Could one do something like: Generate an antibody to the enzyme and then use it to create an ...
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Function of the alpha subunit in mitochondrial ATP-synthase?

Within the catalytic core of mitochondrial ATP-synthase there are two different types of subunits; $\alpha$ and $\beta$. From what I have read, the catalytic sites occur only in the $\beta$ subunit so ...
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Enzyme Inhibitors: Using in vivo in yeast

I find listed on the Sigma-Aldrich site a large list of enzymes & corresponding inhibitors. e.g. For the enzyme squalene synthase the inhibitor listed is "Zaragozic acid A trisodium salt" Would ...
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Does alpha-amylase from different species have different *optimal* conditions?

Do the optimal conditions for the enzyme isoforms differ between species? Specifically, do the optimal pH and temperature for alpha-amylase differ for that enzyme produced by B. lichiniformis and A. ...
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Reason Non linear Lineweaver–Burk plot [closed]

V vs S plot looks like hyperbolic but 1/V vs 1/S plot is not linear at all. Looks like some kind of exponential growth. What can be the reason?
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Does the Michaelis-Menten equation take in account the non-enzyme formation of products?

I only recently learned about the Michaelis-Menten equation, since I am not studying biology or anything related. Let's write the equation as $$\frac{d[P]}{dt} = V_{max} \cdot \frac{[S]}{K + [S]}$$ If ...
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RNAse activity review

I was searching for any review unravelling the structure-function motifs responsible for RNAse activity. Or at least a well-composed review of RNAse superfamilies that are described nowadays (with ...
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Enzymes and Digestion

If biological enzymes (protease,amylase,lipase etc.) just speed up the reaction (in the digestion process), then what actually digests the food?? (I'm a secondary student)
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Enzyme immobilization: Factors that help or hurt success

Are there any factors to consider that can help / hurt the chance to get a successful immobilized enzyme catalyst? i.e. The relative attractiveness of a live host synthesis vs an immobilized enzyme. ...
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Derivation of Michaelis' Equation from Michaelis' Constants [duplicate]

The enzyme reaction condition, $E + S \leftrightarrow ES \rightarrow E + P$ uses $\kappa_{1}$ (forward reaction), $\kappa_{-1}$ and $\kappa_{2}$ as the rate constants. E: Enzyme S: Substrate P: ...
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Difference between negative allosteric regulation and non-competitive inhibition

Both connect to some site other than the active site which controls the shape of the active site and causes the enzyme to be less active. So what is the difference?
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Aspirin - does it inhibit enzyme of thromboxane?

This is a diagram a friend showed me about the drug aspirin, where we were arguing which enzyme it prevents. Aspirin is known to inhibit the production of prostaglandins. However, it also serves fit ...
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Can an enzyme be activated without allosteric inhibition or activation?

Are there ways by which an enzyme may be activated or inhibited by non substrate molecules other than allosteric activation or inhibition?
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Is it possible to separate the binding and catalysis of an enzyme in two steps?

Is it possible to do the following: Enzyme E binds to its substrate S without catalysis; Add a controllable stimulus, such as light, adding or removing chemicals; The enzymatic reaction is triggered ...
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Do we actually know the molecular dynamics of any enzyme?

That is right, is there a limitation, say Heisenberg's uncertainty principle or something that limits our understanding of machinery of enzymes at atomic level? Can we know how do they actually work? ...
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sodium chloride and amylase activity

So, I did an experiment on the effect of sodium chloride on amylase. and I found out the higher the concentration, the slower the activity. Therefore, is it valid to make the assumption that when we ...
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How to calculate the LOB, LOD and LOQ of an enzyme assay

I understand how to calculate limit of blank (LOB), limit of detection (LOD), and limit of quantitation (LOQ) in the traditional way i.e., average and SD of raw analytical signal of blanks and low ...
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Why is binding energy the difference between ∆G catalyzed and ∆G uncatalyzed?

I think the title explains it pretty well -- I'm confused on what 1) exactly binding energy is 2) and why it's the difference. Like in this diagram: my teacher sort of said it was the energy the ...
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Is there a database providing information about optimum temperature and inactive temperature of enzymes?

I want to know optimum and inactive temperature of some enzyme, but I can't find these information in NCBI, wiki or UniProt. So I want to know if there are some database which provide these ...
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Proteases in the blood

I’m reading on hormones and the book talks about how peptide or amine hormones are easily broken down by proteases present in the blood plasma. This has led me to question the interactions between ...
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What's the purpose of Cdk activity having more than one method of becoming inactive?

Cdk becomes partially active once its bound to cyclin and then gets phosphorylated and fully active once a Cdk-activating kinase (CAK) phosphorylates the partially active Cdk. This fully activated Cdk ...
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Affinity Column of membrane bound receptors

I understand affinity columns can be used to study the ligand/enzyme affinity. But is an affinity column able to be used for membrane bound receptors? I

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