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Questions tagged [enzymes]

Enzymes are macromolecular biological catalysts that alter the rate of a reaction. Use this tag for question regarding enzyme kinetics, classification and action.

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Inactivation of enzyme: Why inactivation constants do not follow the Arrhenius equation? [closed]

The Arrhenius equation may not account for the temperature effect on thermal inactivation rate constants. Why can the thermal inactivation kinetics not be expected to follow Arrhenius? The reason that ...
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42 views

How to calculate the kinetic order of an enzymatic reaction?

This question is concerning the metabolism of ethanol by an alcohol dehydrogenase enzyme. Usually people metabolize alcohol equivalent to "one beer per hour". One beer is said to contain 33cL. The ...
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Are enzymes with superior catalytic properties more sensitive to temperature changes?

I am wondering whether enzymes with superior catalytic properties are more or less temperature sensitive than average enzymes. I know that enzymes lower the activation energy, Ea. So the more ...
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2answers
31 views

What's the use of adding 73 mM H2O2 to a supertanant? [closed]

Enzyme assays Determination of catalase specific activity The CAT (EC 1.11.1.6) enzyme activity was measured according to Gallego et al.38 Plant samples were grinded in $\pu{0.1M}\ \ce{...
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28 views

Glucose test strip science project

My daughter is interested in doing an IB science project related to glucose test strips. It has been a little difficult finding references for background review of literature into the chemistry of ...
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1answer
207 views

Is chitin actually protein?

Recently insects are featured as a protein rich source for human nutrition. That humans can really digest chitin through chitinase enzym has been only recently confirmed. But, does the chitin shell ...
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1answer
64 views

What symbol should be used for the Michaelis constant? [closed]

I have found two different abbreviations for the Michaelis constant: $K_\mathrm M$ with capital subscript M, and $K_\mathrm m$ with a regular m. Which form is better for use in an article to be ...
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23 views

Can you discriminate a monooxygenase from other enzymatic mechanisms by the requirement of NADPH?

I am working on a project about CYPs 450. It seems that most of them function as monooxygenases but there are other categories as well. Assuming that the question makes sense, is it correct to say ...
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44 views

What is the Activation Energy of the Hydrolysis of Maltose?

I am trying to determine the reaction rate of the hydrolysis of maltose to glucose in the presence of water using the Arrhenius equation. However, I do not know what the activation energy is. ...
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24 views

Possible reversible inhibition of a cysteine protease (similar mech to serine protease)

I'm trying to work out how this molecule might inhibit cysteine protease. The protease enzyme uses a cysteine residue to nucleophilically attack the carbonyl of an amide bond, and an adjacent ...
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163 views

Application of Michaelis-Menten rate law for biological systems

Many computational models that are used to study biological pathways have been built using Michaelis-Menten(MM) equation. MM kinetics has the assumption that the substrate concentration is much higher ...
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Why is it so hard to turn plastics into something useful or decompose it? [closed]

Even after so many years, why haven't we yet come up with a solution to the plastic problem ? Why are plastics so hard to decompose via chemical or physical processes into something harmless or ...
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What is the difference between transaldolase and transketolase in the pentose phosphate pathway?

What is the difference between transaldolase and transketolase in the pentose phosphate pathway? From what I understand, they both catalyze the transfer of carbon chains from 1 aldose into 1 ketose to ...
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Hill equation, Michaelis-Menten kinetics and bistable kinetics [closed]

I am not a chemist, but a physicist and I am sorry if my question seems stupid to you! I have read about the "Hill equation": it can describe the rate of consumption of a substance. I have also read ...
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1answer
1k views

Why can't amylase digest glycogen?

Amylase is an enzyme that breaks down starch in the form of amylopectin and amylose. Both amylose and amylopectin are formed by alpha glucose joined together by (1-4) and (1-6) glycosidic bonds. ...
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Lowest Michaelis constant Km

I want to find a lower limit of the Michaelis constant for some evaluations of Michaelis-Menten enzyme kinetics. What is the lowest $K_m$ you ever encountered? Is there a theoretical limit?
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What is the correct nomenclature for Glucuronyl C5-epimerase?

I see people writing "Glucuronyl C5-epimerase", "Glucuronyl C-5-epimerase", "Glucuronyl-C-5-epimerase" and "Glucuronyl C5 epimerase", which one is correct? Is there a naming convention?
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Why is fermentation of cellulose to produce biofuel and nutrients so difficult?

The formula for glucose is $\ce{C6H12O6}$ and that of cellulose is very similar $\ce{C6H10O5}$. Glucose can be readily fermented by yeast and other micro-organisms to produce carbon dioxide and ...
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174 views

Derivation of an equality in Michaelis–Menten kinetics

Enzymatic action may be described as follows: $$\ce{Enzyme + Substrate <=>[k_1] ES complex ->[k_\mathrm{2}] Enzyme + Product}$$ The initial rate of enzyme-catalyzed reactions can be ...
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1answer
158 views

How does a hydrophobic environment help in bond formation?

The glucose-induced structural changes are significant in two respects. First, the environment around the glucose becomes more nonpolar, which favors reaction between the hydrophilic hydroxyl group of ...
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1answer
290 views

How do I eliminate the disagreeable odor of soy milk?

I've was making tofu from soy-milk, but noticed this disagreeable odor produced during the process. I conducted a string of internet searches in an attempt to find a method to eliminate this odor. ...
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1answer
199 views

Why does the Michaelis-Menten constant remain constant in the event of non-competitive enzyme inhibition?

A while back, I "answered" the question: Why does the Michaelis-Menten constant decrease in the presence of non-competitive inhibitor? At the time of posting my answer, both the OP and I were under ...
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Thyroid peroxidase - can atomic iodine serve as iodinating agent?

McMurry's Organic Chemistry (7th Ed.) states, that Tyrosine is iodinated by mechanism of electrophilic aromatic substitution and the iodinating agent is $\ce{I+}$ or $\ce{HIO}$ formed by thyroid ...
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Hydrolysis of silk protein

I want to know how you would break down silk proteins into amino acids/peptides, and the end product be almost purely the silk or at least nontoxic for consumption/topical use (dehydrated into a ...
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1answer
217 views

Is it possible to make an anticatalyst?

I'm wondering if it is possible, theoretically, to create compounds which perform the opposite function of a catalyst (thus an anticatalyst). That is to say, could a compound be made which raises the ...
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What is the mechanism that dihydrolipoic acid undergoes to be oxidized by FAD?

The mechanism for dihydrolipoic acid oxidation in the pyruvate hydrogenase complex is not clearly demonstrated in any Lehninger textbook, other than the fact that FAD becomes FADH2. I am wondering ...
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Betaine HCl stomach pH

It seems betaine HCL is often recommended for those suffering from "low stomach acid" -- which, as I understand, is having too high stomach pH for proper digestion (especially for proteolysis via ...
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How to determine the speed of GLUT1 transporter using Michaelis-Menten kinetics?

I am reviewing a passage in my Lehninger Biochemistry Textbook (6th Edition), and the following passage has me very confused. How can one sentence from this passage claim that when [S]out = Kt, the ...
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1answer
72 views

Is histidine drawn wrong in these mechanisms for chymotrypsin?

While trying to understand the mechanism of chypotrypsin, I have been looking at a few mechanisms, which are found in my lecture notes, and one found in my textbook. In both cases, it looks like the ...
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48 views

Calculate optimal surroundings for given reaction mechanism to lower activation energy?

Let's take a reaction that's fairly well understood, which in this case means that the reaction mechanism is known, maybe something like this from here: If we know the reaction mechanism, we also ...
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1answer
132 views

Why does the AraC arabinose sensing system only respond to the presence of L-arabinose?

I understand that when arabinose is present it interacts with araC and changes it shape, promoting the binding of RNA polymerase with the promoter and GFP is produced. However, I don't understand why ...
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2answers
4k views

What is the difference between cofactors and coenzymes?

I've just been wondering what are the differences between the two and I can't seem to find a formal delineation.
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Why does the Michaelis-Menten constant decrease in the presence of non-competitive inhibitor?

Non-competitive inhibitors don't bind to the active sites of enzymes. However, in the presence of non-competitive inhibitors, the Michaelis-Menten constant is found to decrease. Why is this so?
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Thought experiment about nucleic acids oligomerization

A thought experiment: suppose you have managed to contain a pair of nucleic acids in a container in close proximity. How could you encourage oligomerization to occur using only non-enzymatic, physical ...
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1answer
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Is the effectiveness of chemical catalysts affected by temperature the same way enzymes are?

Enzymes do not need high temperatures to function while metal catalysts tend to need a bit of an energy kick to get going. Enzymes will denature, or break, if heated up too far beyond their optimum ...
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Differentiating random and ordered sequential mechanisms in enzyme kinetics

Can random and ordered sequential mechanisms be descern by Lineweaver-Burk plot? Why or why not? Because for orederd sequential mechanism I got different LB plot depending on which substrate is held ...
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930 views

If entropy is decreased when an enzyme-substrate complex is formed, how can the reaction be feasible?

Is it due to the bond formation creating energy that increases the entropy of the surroundings/universe?
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Order of reaction / Rate-determining step in enzyme catalysed reactions

According to my chemistry book, there are 3 simplified steps within an enzyme catalysed reaction: $\displaystyle\ce{S + E -> ES}$ $\displaystyle\ce{ES -> EP}$ $\displaystyle\ce{EP -> E + P}$...
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Word for a specific enzymatic process?

Foreword: I am developing a variable-processing program for my Computer Science research project. One particular part of the program mimics the behavior of biological enzymes, except instead of ...
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660 views

Phosphoglucose isomerase mechanism

The mechanism for phosphoglucose isomerase changing glucose 6 phosphate to fructose 6 phosphate shows histidine protonating the c5 oxygen and lysine deprotonation the c1 oxygen to form an open chain ...
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1answer
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Are imine or amine bonds similar to ethereal bonds, from the perspective of an enzyme?

I'm interested in enzymes that can cleave (hydrolyse or however) an ethereal bond ($\ce{C-O-C}$). Enzymes can evolve to act on chemicals/bonds that are similar to what they previously acted on, so ...
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1answer
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Conversion of enzyme unit (activity) [closed]

Unit Definition: One unit DIAMINE OXIDASE will oxidize 1.0 μmole of PUTRESCINE per hr at pH 7.2 at 37°C. Bio-activity: >= 0.05 unit/mg solid I want to know how much mole of HISTAMINE at same ...
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In the Michaelis-Menten equation for enzyme reaction

In the Michaelis-Menten equation for enzyme reaction, there are two constants Km and Vmax. I know typical values of Km are in the range of 10^-6 ~ 10^-2 M. But I can not find the ones of Vmax. What is ...
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What are some of the more easily manipulated residues on an enzyme?

I am trying to attach a cross-linker to an enzyme and I am looking for candidates for reaction sites. I have several amino acids that are present on the surface of the enzyme (hydrophilic) but I am ...
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Glycogen Hydrolase

Can glycogen hydrolase cleave both glycogen and starch bonds? My intuition says yes because they are both a 1-4(6) glycosidic linkages but I bet I am missing something.
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Effect of His-tag on enzyme activity

In my biochemistry laboratory class, I designed an experiment to study the effect of a His-tag on enzyme activity. First, I measured the activity of the His-tagged enzyme. Then, I cut off the His-tag (...
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3k views

Enzyme Specificity vs Selectivity

Background: I can see a difference in stereoselective and stereospecific reactions in organic chemistry. However, both terms are used interchangeably as synonyms in a biochemistry class. Question: ...
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Calculate the flow rate in the steady state of a dynamic equilibrium

I have the following situation: I am interested of the reactions rate of an enzymatic reaction, depending of the substrate concentration. The thing is, that I don't add the substrate directly to the ...
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2answers
550 views

Binding Energy and Enzyme Rate

I was preparing for the Canadian Chemistry Olympiad and I ran into the following question on one of the past exams: If enzyme A binds to the substrate 25 times stronger than enzyme B, what is the ...
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1answer
561 views

Is it practical to extract zymase from yeast for ethanol production?

Suppose I wanted to make some ethanol fuel. Normally, I would get yeast, mix with water, add sugar and wait. However, there is an enzyme (zymase) in yeast that does this. Looking at the Wikipedia ...