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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26 views

Are some polyketides enzymes?

I am currently reading a "book" (rather an article) called "Protein Modelling & Molecular Docking: Modeller, Autodock". The abstract starts with the following sentence : Polyketides are a ...
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Sugar metabolism in preserved/cryopreserved livestock semen

I wonder how can semen use di/tri-saccharide (e.g. sucrose, trehalose, raffinose) for spermatozoa metabolism in preservation/cryopreservation of livestock semen, since the semen itself never bring any ...
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HELP! How will pH 14 affect enzyme structure? [closed]

If a substance is very alkaline/ basic, e.g. a pH of 14, does this mean that there are near to zero H+ ions (or it is possible to have such a situation where there are zero H+ ions and it is still ...
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In the induced fit model for enzyme action, does the enzyme active site change slightly after products form? [closed]

The reason why I am asking is because I am looking at a past paper and they highlight that it does. I have attached it below. Could you explain why this is the case. I am just looking for a quick ...
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61 views

How does cell detect if a RNA polymerase II is stalled during transcription and in turn deploy the proper transcription-coupled repair factors?

When a segment of the template strand of DNA is damaged due to factors such as UV radiation, a lesion is created that would effectively block the passage of RNA polymerase II during transcription. ...
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What is the protocol for extracting Protease Onion?

I am Investigating the protease concentration in certain fruits and vegetables. I am unable to find the protocols for the extraction from onions. I want to purify my protein using the ammonium ...
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Confusion about mitochondrial electron transport chain Complex I Wikipedia article title

The Wikipedia article title for Complex I (the NADH dehydrogenase enzyme complex) is "NADH dehydrogenase (ubiquinone)". This is confusing to me because this title sounds like ubiquinone is another ...
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How exactly is casein digested?

I mean it seems first step is rennin or pepsin digestion in stomach - then what happens with remaining peptides? I am interested in the whole process from casein to amino acids. Is there brush border ...
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110 views

How can RNAse degrade any RNA?

Every RNA has an unique sequence. Since RNAse is an enzyme and substrates react to its active site in a lock-key mechanism, how is RNAse able to degrade any kind of RNA?
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What are the enzymes with the lowest concentrations in a cell?

Or are there any enzymes which are only translated one time per cell?
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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 ...
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270 views

What molecules does amylase enzyme work on?

I know that in the human body cellulose cannot be broken down by enzymes; however, I am confused as to which molecules amylase enzymes during fermentation. I also looked at https://en.wikipedia.org/...
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270 views

How does BH2 reduction to BH4 need only one NADPH molecule?

Dihydrofolate reductase (DHFR) reduces dihydrobiopterin (BH2) to tetrahydrobiopterin (BH4). Someone told me that this reaction needs only one NADPH molecule (I am not sure if this is correct), namely, ...
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Why is suicide inhibition considered a catalytic reaction when the catalyst is irreversibly modified because of the reaction? [closed]

I understand that this might be meaningless semantics, but I'm confused and would appreciate clarification. I've always been taught that, a catalyst is, by definition, a substance that is increases ...
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41 views

What does ensemble-based model of enzyme mean?

I am reading Pan et al. (2000), a paper about dihydrofolate reductase (DHFR). They claim using a ensemble-based model of DHFR. What is a ensemble-based model?
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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 ...
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What is the active site (not metal binding site) of tyrosinase and other monooxygenase/oxidoreductases?

On https://www.uniprot.org/uniprot/P07524, tyrosinase is shown as a monophenol monooxygenase. However, the UniProt database only shows a metal (copper) binding site, when there is presumed to be an ...
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What is the difference between Leloir and Non-Leloir glucosyl transferases?

The following questions were on the slides for my biotech course and I haven't been able to find any information on what the answer is. What is the difference between Leloir and Non-Leloir glucosyl ...
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Health benefits & enzymes different between Thermophilic and Mesophilic Probiotic cultures?

Is there a difference between the Enzymes produced by Thermophilic vs Mesophilic Probiotic cultures ? are there any other differences in health benefits between the two types of cultures ?
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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, ...
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Is osteoid an uncalcified substance?

I recently learned about Osteoid (the substance secreted by osteoblasts during intramembranous ossification), and I read that it was an "unmineralized organic component of bone." Now, does this mean ...
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646 views

How can some residues in the active site of enzymes be protonated with a pKa < 7?

It is reported in many papers, that some residues in the active site of enzymes need to be protonated to get functional enzyme, where these residues have a low pKa (for let us say 5). How can that ...
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Does pepsin digest plant protein?

This may sound trivial, but... Protein is sourced from plants and animals. Pepsin and HCl digest meat (animal protein). Does pepsin also digest plant-based proteins? I took a look at few articles ...
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What are the differences between isozymes, allozymes and isoforms? [closed]

As far as I have understood Isozymes are derived from different genes but perform similar functions Allozymes are derived from the same gene but different loci, functionally conserved Isoforms are a ...
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355 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 / ...
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What might a supposed “tree enzyme” be — injected into a Morton Bay Fig tree?

I was recently visiting Fremantle in Western Australia and noticed a large Morton Bay Fig tree in Kings square in the centre. Apparently the health of this tree had been declining, but they hope that ...
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What are the chemical characteristics of cofactors that functionally differentiate them from the side chains of amino acids?

Cofactors are essential for the function of many enzymes, such as NAD+ in the glycolytic pathway - I was wondering how the chemical properties of these cofactors allow them to fulfil their function ...
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285 views

Is the Insulin Receptor Considered an Enzyme?

Can we consider insulin receptor an enzyme? In other words, does the insulin receptor have enzymatic characteristics?
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Screening Enzymes?

I wish to obtain a list of all known enzymes and then get rid of the ones that use cofactors, the ones that use ATP, and a few others. What is the easiest way to do this?
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297 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 ...
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278 views

Could removing non-functional parts of coenzymes improve enzyme function?

As pointed out here, many important co-enzymes (essential enzyme cofactors) such such acetyl-CoA and vitamin B12 contain nucleotide portions that do not function in the enzyme catalysis. They have ...
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If humans had cellulase would they be able to digest grass?

Cellulase is an enzyme capable of breaking cellulose. If humans were able to produce cellulase in our stomach would we be able to digest grass? If not, what more things would we need in order to ...
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743 views

Which enzyme curdles milk in human infants? [duplicate]

Following, this question - Do humans produce rennin? Rennin does not exist. And What inactivates pepsin in infants? Rennin exist. What do I know is- Rennin is found in calves and acts on milk to ...
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49 views

What does metal-dependent mean?

I was reading about Cas1 and Cas2 and came across this excerpt: ...Cas2 was identified as a metal-dependent endoribonuclease that cleaves ssRNA or dsDNA... What does metal-dependent mean in this ...
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2k views

Non competitive inhibitors and Uncompetitive

Non competitive inhibitors affects the function of enzymes and slows the rate of reaction. Can I say the same for uncompetitive inhibitors ? Because Vmax decreases and it takes longer to form products ...
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Can methionine peptidase liberate selenomethionine?

Can methionine peptidase liberate selenomethionine from proteins? I'd be happy to know if any can that are active in humans, but am also especially curious about METAP2.
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Please explain this notation MW around 9 MDa

I am a computational science student and was reading about the structure of Pyruvate dehydrogenase (PDH). link to article The article mentions "PDH is a large complex (MW around 9 MDa) consisting of ...
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Is there a hypernym for enzymes that “cut” other molecules?

I have searched on Google for a hypernym/umbrella term that encompasses all enzymes whose function is to cut other molecules, but I have yet to find such a term. The term I am looking for would ...
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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 ...
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Can cognitive enhancement from exercise be replicated/replaced through prolonged standing?

Can cognitive enhancement from exercise be replicated/replaced through prolonged standing? Like, will BDNF be released from prolonged standing. I would prefer to use a standing desk than exercise (...
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What enzymes I shall use for preparing single cell suspension from cardiac tissue for flow cytometry?

Can anyone suggest which enzymes I shall use for preparing single cell suspension from cardiac tissue. I will be looking at both cell surface and intracellular antigens involving cardiomyocytes and ...
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Are there any alternatives to the Epicentre product Plasmid Safe?

I need to remove any traces of linear DNA (both single and double stranded) from a ligation reaction while keeping circular DNA intact. Up to now, I have used Epicentre's Plasmid Safe to do the job. I ...
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Triosephosphate isomerase deficiency

Triose phosphate isomerase deficiency, a rare condition, is the only glycolytic enzymopathy that is lethal. This deficiency is characterized by severe hemolytic anemia and neurodegeneration. How can ...
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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 ...
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153 views

Do different chiral centers on ligands cause different confirmational changes and effects in their target proteins?

Say pathogenic bacteriaA makes toxinA, which had D-amino acids instead of L-amino aids, does this difference in chirality cause a different conformational change in the receptor or enzyme, thus ...
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Is starch and glycogen digestion intra or extracellular?

Do humans have the enzyme for starch intracellular digestion? Also, do plants have the ability to digest Glycogen? Intra or extracellular, or both?
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Can enzymes catalyze thermodynamically unfavorable reactions?

Can biological enzymes catalyze thermodynamically unfavorable reactions? I read that an enzyme lowers the activation energy of a reaction by offering an alternative reaction pathway with a lower ...
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3k views

How does aminoacyl-tRNA synthetase recognize different tRNAs?

There are about 20 aminoacyl-tRNA synthetases, one for each amino acid. Each aminoacyl-tRNA synthetase has a binding site that recognizes a specific amino acid, and other binding areas that recognize ...
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Why is chloride ion classed as a cofactor for amylase rather than as a coenzyme?

I am provided with the two following statements and have to prove which is true and which is false. $\ce{Cl-}$ acts as a coenzyme for amylase $\ce{Zn^2+}$ acts as a prosthetic group for carbonic ...
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Energy cost of chewing vs production of enzymes

Consider a hypothetical case that you ingest a piece of starch. Which is more costly energetically 1) chewing + reduced amount of enzymes production needed or 2) sole production of all the enzymes for ...

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