Questions tagged [enzyme-kinetics]
Enzyme kinetics are the studies of the biophysical properties of enzymes and their substrates.
75
questions
0
votes
0answers
18 views
Cellulase enzyme [closed]
I have read that B-glycosidase enzyme can break b-glycoside link using the carboxylic group in it. So can acetic acid or any carboxylic acid induce the same effect. I tested this by putting paper in ...
2
votes
1answer
62 views
Enzymes extracted from diferent tissue, may have diferent $K_m$ values under the same conditions?
My laboratory team has been used succinate dehydrogenase (1.3.5.1) from Gallus gallus domesticus breast (the most meated part of the chicken, where you will obtain nuggets) to determine $K_{m}$ and $...
2
votes
1answer
46 views
Do there exist enzymes that can take up multiple cofactors to do different reactions?
I was thinking about enzyme catalysis, and it seems like enzymes can only catalyse one kind of forward/reverse reaction (please correct me if I am wrong). Does there exist an enzyme that can catalyse ...
0
votes
0answers
35 views
When do enzymes catalyze reaction of both direction and when do they not? [duplicate]
I've read that enzymes can catalyse both forward and backward reaction so they don't change eqm position etc.
However protein kinase catalyses phosphorylation, while phosphatase catalyses ...
1
vote
1answer
66 views
How could pharmaceutical metabolizing bacteria be used to synthesize them?
Lets say I have a pharmaceutical "P". It can be broken down by enzymes of one strain of bacteria into two molecules one of which can be further metabolized enzymatically by a different strain of ...
0
votes
0answers
31 views
Adzuki vs Black Beans vs Soy Nattokinase Content?
Is anyone familiar with whether or not Adzuki Beans, Black Beans or other such fermentation substrates contain similar levels of Nattokinase as would the traditional Japanese Soy Bean Natto? Is there ...
2
votes
0answers
48 views
Which enzyme is Nick Lane referring to?
In Life Ascending the author, Nick Lane, refers to an enzyme in his introduction:
'' It concerns an enzyme (a protein that catalyses a chemical reaction) that is so central to life that it is found ...
-2
votes
1answer
317 views
-2
votes
1answer
1k views
How to calculate the turnover number?
I understand that Kcat (turnover number) = Vmax/total enzyme concentration.
However the formula I have been given is Kcat = specific activity/molecular mass of enzyme.
What is the relationship ...
0
votes
1answer
69 views
Struggling to make sense of Km [closed]
So I have two substrates for one enzyme and I measured the product formation-> michaelis menten kinetics. The Vmax for both substrates is the same, the Km however is higher on substrate number 2. ...
-2
votes
1answer
54 views
Michaelis Menten kinetics - Plotting to find V-max and Km [closed]
In dealing with the question above I know that if we plot 1/v against 1/[isocitrate] we can get V-max = 1/intercept and Km = slope/intercept.
However when I express the two rows of values in ...
5
votes
1answer
337 views
Michaelis-Menten equation; how to find the constants from enzyme activity experimental results?
I was wondering what the constants in the Michaelis-Menten equation actually mean in experimental data of enzymes. How do I process the data to find Km and Kcat?
I did an experiment on catalase and ...
2
votes
0answers
316 views
How to convert between Kunitz units and Enzymatic units?
I've googled around and there has been the common answer of 1.5 U = 1 Kunitz Unit, but none of those answers have come from a reputable source, so I am really doubtful. :(
The enzyme I use comes in ...
0
votes
1answer
68 views
What is the dependent variable of a relative fluorescence graph?
So it was asked what was the dependent variable of this experiment. I know that as students, we're wired to think that the y-axis is the dependent variable while the x-axis is the independent variable ...
1
vote
0answers
17 views
Determining the Value of Inhibition constant
I am trying to understand how the inhibition constant is calculated for competitive inhibition.
$\frac{K^{app}}{V^{app}} = \frac{1+I/K_i}{V/K_m}$.
But often in secondary plots, $\frac{K^{app}}{V^{...
1
vote
1answer
94 views
The threshold of Ki
Is there any threshold (Ki) between strong and week small molecule inhibitors?
When I see the (Ki) values in any published work, how can I decide if this good or bad inhibitor?
2
votes
0answers
16 views
What is the concentration/molecules per cell of iodothyronine deiodinase in a cell?
I'm trying to parameterize an in silico model and need the approximate concentration (M), or molecules per cell, of iodothyronine deiodinase type II (D2) enzyme in a human cell, ideally a glial cell. ...
2
votes
1answer
50 views
What does enzymatic equilibrium in % represent?
I am studying an enzyme which can catalyse a chemical reaction in both directions. The paper I am looking at is mentioning a thermodynamic equilibrium of 1% in the synthase direction.
What does that ...
1
vote
1answer
2k views
Can lysozyme also lyse gram-negative bacteria and if yes, how fast?
Lysozyme attacks peptidoglycan, which are found in Gram-positive bacteria. I know someone who uses lysozyme to lyse Escherichia coli, which is Gram-negative. How is that possible? Can lysozyme lyse ...
2
votes
0answers
36 views
Measuring Enzyme Kinetic constants
Is it possible to experimentally determine $k_1$ and $k_{-1}$ of the Michaelis Menten model:
$\ce{E + S <-->[k_1][k_{-1}] ES ->[k_{cat}] E + P}$,
or their ratio?
1
vote
2answers
124 views
How can ionized amino acid form be important for the catalytic activity?
I can imagine that protonated amino acid form, particularly at the active site, is important for the catalytic activity so hydrogen bonds can be created between the substrate and the enzyme. However, ...
1
vote
0answers
314 views
Specific activity vs turnover number of enzymes in BRENDA
From my understanding, the specific activity (A, units: umol/min/mg protein) can be derived from the turnover number (k, units: 1/seg) and the molar mass of an enzyme (MW, units: g/mol):
A = k / MW / ...
1
vote
2answers
243 views
What are the structural factors affect enzyme's Km?
Is there any rules (should not be exact), to estimate the kinetic changes in an enzyme if I did any mutation on it?
If I cannot estimate the new kinetic values, is it possible at least to clarify or ...
4
votes
2answers
365 views
Enzyme kinetics at the chemical level
I am stumped by two questions:
Why do we take only the initial 10%(or may be 9.99999....%) of S conversion as the rate of the enzyme reaction. why not more than 10%?
Why doesn't the velocity keep on ...
2
votes
1answer
633 views
Gibbs free energy and entropy in enzyme catalysis
In enzyme catalysis, the formation of the enzyme-substrate complex causes a reduction in the entropy of the system. If entropy reduces, the gibbs free energy will become less negative. How then is ...
1
vote
0answers
27 views
Assay for Glycosyltransferase
I want to do an assay to see, if an ordered enzyme is active or not. It's a glucosyltransferase from S. mutans which hydrolyses sucrose into fructose and glucose. It then connects the glucose-monomers ...
9
votes
1answer
1k views
Understanding Enzyme saturation curve
From the above picture it can be seen that, in the region "B" the activity of enzyme is not proportional to the substrate concentration.
Why don't we achieve enzyme saturation linearly? Why do we go ...
2
votes
0answers
97 views
Kinetics of allosteric regulation [duplicate]
I have found a diagram similar to the following one in my biology textbook. The diagram describes allosteric regulation.
However, I do not quite understand why the maximum reaction rate $V_{max}$ is ...
2
votes
2answers
299 views
Is the affinity of an enzyme or transporter for its substrate or solute influenced by the amino acids at the binding site?
The affinity of an enzyme or a protein transporter indicates the strenght of the binding of substrate/solute. An enzyme with higher affinity binds its substrate more strongly than a counterpart with a ...
4
votes
2answers
1k views
Identifying type of inhibitor from $K_m$ and $V_{max}$
Apparently it is possible to identify whether an inhibitor is competitive or non-competitive from graphs of substrate concentration (x axis) and rate of reaction (y axis).
There needs to be a line ...
5
votes
1answer
140 views
How to derive rate of product formation for an allosterically inhibited enzyme?
I'm working through Mathematical Modelling in Systems Biology: An Introduction by Brian Ingalls, and in Chapter 3 there's an example of a simple allosterically inhibited enzyme with reaction scheme ...
4
votes
1answer
145 views
How does hydration affect digestion?
My textbook( biochemistry by Satyanarayana, 4th edition pg.no:166) says:
The polysaccharides get hydrated during heating which is essential for their efficient digestion.
(I think there is a typo ,...
2
votes
1answer
269 views
Enzyme kinetics types?
In lectures, we have discussed Michaelis Menten enzyme kinetics, but from lectures it was clear that this was not the only type of kinetics.
After looking into this, I have found enzymes that give a ...
2
votes
1answer
65 views
The effect of 3D structure and solubility of the binding site of enzyme on its affinity Km and maximum activity Vmax? [closed]
Could some one provide me with some resources or papers where I can read more about the following:
1- How can the 3D structure of an enzyme affect its Km and Vmax? (some papers, books or articles ...
1
vote
2answers
2k views
Why half of the protein is saturated when [L] =Kd
let's suppose the following reaction:
At equilibrium we can calculate the Kd (Dissociation constant) using the following formula:
Kd = [P][L] / [PL] or kd / ka
We can then use the Hill equation to ...
3
votes
2answers
39k views
What is the meaning behind Kcat / Km?
I'm trying to understand enzyme kinetics, the formula for Km and Kcat make sense to me.
Km , the substrate concentration at which the reaction rate is half of Vmax
Kcat, used to describe the ...
2
votes
1answer
2k views
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 $ \...
1
vote
1answer
38 views
Enzyme with long tube leading to active site?
Are there any enzymes that force one or more of their substrates to travel a relatively long distance through a small opening/tube through the enzyme and to the active site? (not a transport protein)
2
votes
1answer
54 views
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 ...
5
votes
0answers
183 views
How can some enzymes work faster than the diffusion rates of the molecules it catalyzes allow? [closed]
Quoting Wikipedia: "Some enzymes operate with kinetics which are faster than diffusion rates, which would seem to be impossible." Which are those enzymes and how can they be so fast?
One example is ...
0
votes
0answers
26 views
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. ...
2
votes
1answer
12k views
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 ...
0
votes
1answer
47 views
Ways to monitor enzyme kinetics with very fast time resolution?
I'm interested in any way to do time-resolved study of enzyme kinetics. I am studying some physical variables that may affect kinetics, but I want to study how quickly they take effect, and how long ...
1
vote
0answers
19 views
Glucose Oxidase, Condition to be Active?
I most recently was reading/watching information on honeys antibatical and antimicrobial properties. The enzyme Glucose Oxidase came up often as a main antimicrobial, yet it is inactive in honey. ...
1
vote
1answer
232 views
Enzyme kinetics: recommended literature to grasp the concepts better
I have had a few biochemistry courses, but I still feel confused and a bit scared each time they try to explain and apply enzyme kinetics or even chemometrics in different situation during class. On ...
2
votes
1answer
1k views
Enzyme kinetics: Effect of immobilization on kinetic parameters
What is the typical effect of enzyme immobilization on the kinetic parameters of an enzyme's activity?
Can one assume that they'd stay approximately the same or is there a gross change? Any way to ...
0
votes
1answer
2k views
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?
2
votes
1answer
82 views
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 ...
6
votes
1answer
3k views
Why is competitive inhibition reversible?
My Biochemistry book mentions that 'competitive inhibition' is a reversible form of inhibition. But given that the inhibitor is blocking the active site and prevents an enzyme-substrate complex to be ...
2
votes
0answers
624 views
Convert flux value in nmol/min/mg protein to nmol/min/cell?
This is a question about unit conversion. I found an experimental measurement of the saturation uptake of glucose in yeast:
$$V_\textrm{max} \approx 650 \textrm{nmol}/\textrm{min}/\textrm{mg protein}$...
