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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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 an example of chemical reaction that can be assisted by both an inorganic catalyst and an enzyme?

I have been researching chemical reactions of inorganic catalysts and enzymes and cannot find a chemical process where an inorganic compound can be replaced by an enzyme (or vice versa) and have the ...
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AChE Aging time of organophosphorus compounds containing hydroxyl groups

Organophosphorus compounds are known to inhibit the enzyme acetylcholinesterase (AChE). This occurs when the OPC phosphorylates the serine-203 residue of the enzyme. If the enzyme is not reactivated ...
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Influence of Temperature on Biochemical Reactions [closed]

Short question How (quantitatively speaking) does temperature influences rate of decay of proteins? I am looking for some general number/function, the influence of temperature on an average protein. ...
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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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Can a very high concentration of hydrogen peroxide, inhibit or denature the enzyme catalase?

My experiment, where I am investigating the effect of increasing substrate concentration of hydrogen peroxide on enzyme activity hasn't worked out as I hoped. The last result, highest concentration of ...
George's user avatar
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Why use Km in catalytic efficiency?

The catalytic efficiency of an enzyme is given by $k_{cat}/k_M$ where $k_{cat}$ is the turnover number, or the number of molecules that can be produced per second per active site of an enzyme. $K_{M}$ ...
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How does fluorouracil inhibit thymidylate synthase?

I'm curious to know how just by adding a fluorine atom to uracil (to form 5-fluorouracil) permanently inhibits the enzyme thymidylate synthase when they bind together. This molecule is widely used as ...
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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 ...
Jonathan Smith's user avatar
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How can subtilisin still function without its catalytic triad?

I read chapter 9 in the book Biochemistry (5th edition), by Berg, Tymoczko, and Stryer (provided in the NCBI site here). It describes the mechanism of action of the chymotrypsin enzyme. The catalysis ...
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The Propinquity Effect

I am currently in the process of studying enzyme catalysis and am struggling to get to grips with this concept. As far as I understand, the propinquity effect allows substrates to bind with enzymes in ...
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Is a hydrocarbon bio-battery feasible?

Hydrocarbons have some of the highest energy densities and specific energies of any chemical fuel. Unfortunately, our primary use of them is in thermal engines, whose efficiency is limited by Carnot'...
Lawnmower Man's user avatar
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Why do so many biochemical reactions require enzymes?

Studying biochemistry as part of the Great Courses, I am struck that all 10 steps in glycolysis require an enzyme. I’d have thought that evolution would have selected for a “simpler” pathway with ...
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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 ...
0tyranny0poverty's user avatar
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Why does aldolase not act upon glucose-6-phosphate?

I was recently asked to explain why (fructose-bisphosphate) aldolase does not act on glucose 6-phosphate in glycolysis and waits until the formation of fructose 1,6-bisphosphate. I did not know much ...
AvadaMouse's user avatar
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3 answers
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Representation of bromelain molecule in two dimensional diagram [closed]

If I'm not wrong, I learned in 2011 introduction to neuropsychology course that all enzymes are proteins. As far as I know, any protein, not even the smallest of the TAL group (which I understand to ...
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What is the fate of sulfur in cysteine when it participates in gluconeogenesis?

Amino acids can be broken down to yield pyruvate, which in turn can be used to construct glucose molecule in the process of gluconeogenesis. What happens to the sulfur atom in the amino acid cysteine ...
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What makes something biodegradable?

Learning about biodegradable polymers and non-biodegradable polymers. What exactly sets them apart though? Here's the formula from wikipedia for the biodegradable PHB: and here for polypropylene, it'...
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Where to find compounds IC50 on an enzyme?

I am looking for half maximal inhibitory concentration (IC50) values on a enzyme. I already searched through ChemBL, PubChem and BindingDB. The three seem to give consistent results. However, ...
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How does the human body process Bromelain in pineapple? (A meat tenderising/dissolving enzyme)

It turns out pineapple juice can dissolve a jello set, and turn a beef roast to paste. It turns out this is caused by Bromelain, an enzyme sometimes used in meat tenderising. I'm trying to work out ...
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Finding specific activity of an enzyme from Km values for a reversible enzyme reaction

I have an enzymatic equation in the form: $$E + S\xleftrightarrow[k_{-1} = 2.6\text{ x }10^{-2} \text{s}^{-1}]{k_1 = 3 \text{ x }10^8 \text{M}^{-1}\text{s}^{-1}} EX \xleftrightarrow[k_{-2} = 3.8\text{...
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Does the mechanism of AChE inhibition by Isoparathion depend on chirality?

It is known that the inhibition of acetylcholinesterase by isomalathion can proceed either with diethyl succinate as the leaving group or thiomethyl, depending on the specific stereoisomer of ...
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When an enzyme is diluted with water, what is slowing down the rate of reaction?

I'm specifically talking about the decomposition of hydrogen peroxide by bovine catalase. The number of catalase molecule obviously doesn't change, so there's the same number of catalase molecule ...
Long Vuong's user avatar
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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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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 ...
paracetamol's user avatar
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What is a secondary shell in an enzyme?

I've searched the internet for a definition of what the different shells in enzymes/proteins are and haven't found a good answer. This Nature article, which is about an enzyme that catalyzes Kemp ...
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Why does allosteric binding produce a sigmoidal curve?

Allosteric binding is where the enzyme can be regulated through having ligands bind onto somewhere that is not the active site. This will then induce a conformational change on the active site, hence ...
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Does migraine medicine Topiramate work by supplanting Pyridoxal phosphate in enzymes?

I have seen it said that the precise mechanism of action of migraine medicine Topiramate is not known. But I certainly see a resemblance between that molecule and PLP (Pyridoxal phosphate, the ...
user240254's user avatar
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How do enzymes affect a reaction's equilibrium?

I am not sure to understand something I read in a educational journal (1) Introduction Lets consider the following reversible enzyme-catalysed reversible reaction; $$E + S \leftrightharpoons ES \...
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Why are S-thiocarbamates less toxic than carbamates?

According to Haley and Rhodes, neostigmine bromide (alternatively known as Prostigmine) has an LD50 in mice of around 0.165 mg/kg by IV injection. Pubchem claims that this is also the LD50 for ...
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Interaction of trifluoroacetates with acetylcholinesterase

There exists a substance called TMTFA, or 3-(N,N,N-Trimethylammonio)-2,2,2-trifluoroacetophenone. It is known for being able to inhibit acetylcholinesterase at femtomolar concentrations. The TMTFA-...
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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 ...
JM97's user avatar
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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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Conservation equation in an enzyme-catalysed reaction

Consider the reaction scheme: $$\ce{S + E ->[k_1] C1} \qquad \ce{C1 ->[k_2] E + P} \qquad \ce{S + C1 <=>[k_3][k_4] C2}$$ where $\ce{S}$ is the substrate, $\ce{E}$ is the enzyme, $\ce{P}$ ...
Michael Howlard's user avatar
4 votes
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127 views

What is the mechanism of AChE inhibition by Onchidal?

A naturally-occuring neurotoxin, called Onchidal, produced by a species of sea slug acts as an irreversible inhibitor of acetylcholinesterase. The structure of Onchidal is presented below: How and ...
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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 ...
David's user avatar
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Enzyme Kinetics

How come enzymes with a lower $K_\mathrm{m}$ are more easily saturated with substrate than an enzyme with higher $K_\mathrm{m}?$ Is it because enzymes with higher $K_\mathrm{m}$ are able to bind ...
Ahmer Imam's user avatar
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Why are isomers of parathion less active acetylcholinesterase inhibitors than paraoxon?

Parathion itself has been found to be a very weak inhibitor of acetylcholinesterase. It normally requires metabolic activation and the conversion into paraoxon in the body to actually start exhibiting ...
user73910's user avatar
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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 ...
user30150's user avatar
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1 answer
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Why can we not use water instead of blank control solution in enzyme catalysis with Peroxidase experiment?

I have to do a lab about enzyme catalysis with peroxidase in my chemistry class. We are to use the blank control solution in the experiment. My question is, why can we not use water instead? I did ...
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Spectrophotometric assay by pNPP

Here is a series of related questions that I want to ask. Background The activity of acid phosphatase is measured by an enzymatic reaction that converts para-nitrophenyl phosphate (pNPP) to para-...
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If no oxygen is present, will cut avocados stop browning?

Oxygen makes cut avocados brown, or at least it is necessary to facilitate the rapid browning reaction we see within 24 hours of cutting the avocados. If oxygen was completely removed from the air ...
Daniel's user avatar
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Are there natural enzymes that catalyze different reactions under different conditions?

Are there natural enzymes that catalyze different reactions under different conditions? For example an enzyme undergoes a conformational change under certain pH and starts catalysing a different ...
Euphorbium's user avatar
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Can bis-quaternary aromatic compounds act directly on acetylcholine receptors?

The book Cholinesterases and Anticholinesterase Agents gives examples of bis-quaternary aromatic compounds that are capable of inhibiting acetylcholinesterase. Page 400 gives examples of some such ...
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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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4 answers
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Why is the units of kcat 1/s?

I understand that $k_\text{cat}$ measures the turnover number of an enzyme. This measure is therefore a quantity of molecule conversions per unit of time. I suspect that my problem is more that of a ...
CiaranWelsh's user avatar
3 votes
2 answers
203 views

How is NADH or NADPH produced in industrial chemical synsthesis?

I am trying to find out how NADH or NADPH are produced in bulk. These molecules are very important biologically, however, they are also sold as chemical reagents and produced in large quantities. How ...
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PLP-Dependent Cyclization and Decarboxylation

I am looking at Compound A (see below) and am trying to figure out a decarboxylation mechanism that results in Compound B (see below). I have come up with an internal mechanism that might work that I ...
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Effect of competitive inhibitor on substrate inhibition

In an enzyme that undergoes substrate inhibition, how would the presence of a competitive inhibitor affect said substrate inhibition? Would the substrate concentration at which substrate inhibition ...
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Can lipases cleave fatty acids linked with amides instead of the usual esters?

The typical substrate for lipases are esters, such as triglycerides where fatty acids are linked to the glyerol through ester linkages. I'm interested in whether lipases (such as pancreatic lipase) ...
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