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7 votes

Identifying type of inhibitor from $K_m$ and $V_{max}$

I think it is possible to identify the type of inhibition from (initial) velocity vs substrate-concentration curves, but it is difficult. The usual way this is done is by using a linear transformation ...
user338907's user avatar
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7 votes

Enzyme kinetics at the chemical level

The answer to the first part of your question is that we don't take the initial 10% of a progress curve (velocity vs time) as a measure of activity, but we measure the initial rate of the reaction. ...
user338907's user avatar
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Identifying type of inhibitor from $K_m$ and $V_{max}$

Competitive inhibitor competes for the active site. Therefore it will interfere with the binding of the substrate thereby increasing the apparent KM. A strictly non-competitive inhibitor does not ...
WYSIWYG's user avatar
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Effect of pH, temperature and enzyme concentration on Km

Michaelis constant is defined as $$K_\textrm{M} = \frac{k_{-1}+k_2}{k_1},$$ where $k$s represent the rate constants for the reactions $$\mathrm{E+S} \;\;\underset{k_{-1}}{\overset{k_1}{\...
Domen's user avatar
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Can lysozyme also lyse gram-negative bacteria and if yes, how fast?

Gram-negative bacteria also have peptidoglycan which can be degraded by lysozyme. However they have an outer membrane lying outside the peptidoglycan layer and this will block lysozyme action. ...
Alan Boyd's user avatar
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5 votes

Is the affinity of an enzyme or transporter for its substrate or solute influenced by the amino acids at the binding site?

In a reaction which follows a saturation kinetics, KM is basically the concentration of substrate/ligand at which the rate of the reaction is half of the maximum rate (or the binding sites are half ...
WYSIWYG's user avatar
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Why does uncompetitive inhibition decrease the Michaelis constant?

First off, the difference between the types of inhibition: competitive inhibition: The inhibitor only binds to the substrate-free form of the enzyme. (Not necessarily at the active site!) ...
R.M.'s user avatar
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Enzymes extracted from diferent tissue, may have diferent $K_m$ values under the same conditions?

You would not expect the same enzyme from different tissues to have different Km values if the enzymes are truly identical. In addition, you would not expect the Km value to change during ...
user338907's user avatar
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Why does an Enzyme-Substrate Complex have slightly less energy than the substrate alone?

The diagram presented in the question is only one of many variations found in text books and the like. It is unsatisfactory to the extent that it shows one of the intermediates (ES) in the catalysis, ...
David's user avatar
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What is the meaning behind Kcat / Km?

Just as $k_{cat}$ represents the rate of reaction at saturating substrate concentration, $k_{cat} / K_m$ represents the rate of the reaction at negligible substrate concentration. If we take a look ...
R.M.'s user avatar
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What are " temporal kinetics"?

Temporal kinetics does not refer to the kinetics of kinase phosphorylation reactions and, since it is not standard terminology, you likely wouldn’t find its meaning in any textbook. The authors of the ...
canadianer's user avatar
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4 votes

Why such strange enzyme kinetics?

Worth considering whether it is an effect of the instrument or the system. What would happen if you preincubated your plate for 10 minutes? Would you have the "dip" after 25 minutes or again ...
Bjarte Lund's user avatar
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Reversal of reactions and enzyme catalysis

There are two things to consider in relation to an enzymic reaction. The rate is one consideration, but that has no influence on the direction in which the reaction proceeds. The direction in which ...
David's user avatar
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How to calculate the turnover number?

Let's do some unit analysis: $\pu t$ = time $\pu U$ = units = $\mathrm{mol_{product}/t}$ $\pu s=$ specific activity $\mathrm{= U/g_{protein}}$ Therefore: $\mathrm{s = mol_{product} / (g_{protien} \...
J--'s user avatar
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What does enzymatic equilibrium in % represent?

You are correct in stating the relative rates of the two reactions. What may have you confused is the percent sign in the statement. The percent sign is not a unit in the sense that you are taking ...
Edward Kowal's user avatar
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Enzyme kinetics: recommended literature to grasp the concepts better

I always used the book "Enzyme Structure and Mechanism" by Alan Fersht. (Structure and Mechanism in Protein Science: A Guide to Enzyme Catalysis and Protein Folding is the latest version, published in ...
VonBeche's user avatar
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In the Lineweaver-Burk Plot, why does the x-intercept = -1/Km?

Set $ \dfrac{1}{V} = 0$ and solve for $\dfrac{1}{[S]}$: $ 0 = \dfrac{K_m}{V_{max}}\dfrac{1}{[S]}+ \dfrac{1}{V_{max}} $ $ -\dfrac{1}{V_{max}} = \dfrac{K_m}{V_{max}}\dfrac{1}{[S]}$ $ -1 = {K_m}\...
notorious's user avatar
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Enzyme with long tube leading to active site?

First of all, as you mentioned, there are a lot of membrane / transport proteins with very nice, well defined tunnels. But you're looking for a soluble / cytosolic enzyme. Some oxygen-dependent ...
VonBeche's user avatar
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Do there exist enzymes that can take up multiple cofactors to do different reactions?

It sounds like you are asking about what are commonly referred to as "multifunctional enzymes". For a reasonably recent article covering this subject — see: Cheng, X. Y., Huang, W. J., Hu, S. C., ...
tyersome's user avatar
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Is there an enzyme that functions without being associated with a complex?

Acetylcholinesterase. Chosen because the esterase seems like a low energy reaction so it wouldn't need energetic co-factors. https://en.wikipedia.org/wiki/Acetylcholinesterase Not sure if I should do ...
Polypipe Wrangler's user avatar
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Meaning of some unit of measurement of kinase activity

It is not a specific unit of kinase activity, rather a general approach taken for following reactions where there is no change of colour. The abbreviation cpm stands for counts per minute and is a ...
Bjarte Lund's user avatar
3 votes

What other sites do non-competitive inhibitors bind to apart from allosteric sites?

Here is a helpful excerpt from the lecture notes for Introduction to Molecular and Cellular Biology at Columbia University, taught by Lawrence Chasin and Deborah Mowshowitz (emphasis mine): Re: ...
acvill's user avatar
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3 votes

How does one derive a KD from an equilibrium titration experiment?

The models you are using are based on the Langmuir Isotherm. The classical use of this model is for gas adsorption to a solid. In these experiments, the pressure of the gas is measured against the ...
stords's user avatar
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The effect of 3D structure and solubility of the binding site of enzyme on its affinity Km and maximum activity Vmax?

Probably the big reason you were unsuccessful in your previous searches is that nobody quite knows exactly how enzymes' 3D structures lead to particular kinetic parameters. It's wrapped up in the ...
R.M.'s user avatar
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2 votes

What is the use of futile reaction cycling such as Fruc-P to Fruc-BP?

Phosphofructokinase 1 (PFK 1) is not rate-limiting, its flux control coefficient when measured is invariably small. The fact that textbooks keep suggesting the PFK is rate-limting is just a textbook ...
rhody's user avatar
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2 votes

How to derive rate of product formation for an allosterically inhibited enzyme?

If you apply quasi-steady state approximation for the complexes then you will get three equations for each of the complexes. Then you have to use the conservation law for enzyme to obtain the equation ...
WYSIWYG's user avatar
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2 votes

Gibbs free energy and entropy in enzyme catalysis

As @canadianer hinted, the answer is enthalpy. ΔG = ΔH - TΔS For binding to be a spontaneous process ΔG must be negative. If the binding of a ligand to a protein decreases system entropy then ΔS is ...
Alan Boyd's user avatar
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2 votes

Enzyme kinetics at the chemical level

The kinetics of enzyme catalysed reactions is a specialized area of biochemistry. It was historically important when much less was known about enzymes and the tools for studying them were limited. Why,...
David's user avatar
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