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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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Do mammals use uricotelic excretion?

Mammals use the enzyme xanthine oxidoreductase to oxidise purines to uric acid. Then, uricase is used to convert uric acid to allantoin. If they are able to do this, then why do we say that mammals ...
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substances in biology in an argument

When Maltase and maltose are combined what does it make? My friend and I are in a argument. She says that you are supposed to combine maltase and Glucose if so what does that make? (what is the ...
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Do we know how dangerous six-eyed sand spiders are?

The Sicariidae family contains the well-known and dangerous Loxosceles spp. (fiddle-backs, violin spiders). The family's other two genera, Sicarius and Hexophthalma (six-eyed sand spiders) have ...
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Are all enzymes proteins?

So throughout my education and research career I have been taught that all enzymes are proteins. This makes sense when you consider enzyme denaturing and folding/shape etc. However, I was recently ...
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Are there any enzymes without aromatic amino acids?

I'd like to try a new spectroscopic technique to study enzymatic reactions (which reaction doesn't especially matter, something simple and with fast kinetics like catalase would do fine - I'm just ...
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59 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 ...
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How can we quantify the effect of pancreatin (biological enzyme) on the clarification of milk powder

Alright so I'm trying to quantify the rate at which casein (protein constituent of milk powder) is converted into a product (I am unaware of) by pancreatin (a biological enzyme that speeds up the ...
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What are the effects of enzyme exposure to high temperatures? [duplicate]

Question: After enzymes are exposed to high temperatures and undergo denaturation, then returned to their optimal temperature and renatured, can the enzyme's active site return to it's original shape ...
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Why does M1 RNA together with C5 protein in 100mM Mg(II) fail to cleave tRNA?

Sidney Altman discovered that RNA moeity of RNAse P (M1 RNA) alone is able to perform enzymatic cleavage of ptRNA, which won him the Nobel Prize of Chemistry in 1989. However, when I read the Nobel ...
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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 ...
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Can sucrase catalyze the breakdown of maltose?

Since sucrase is the enzyme that breaks down sucrose into glucose and fructose. Will sucrase also catalyze the breakdown of disaccharide maltose?
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Why are plants unable to take up Phosphorus directly in their organic form like Phytic Acid?

I am researching acquisition strategies of phosphorus by decidious trees. I am reading a lot that plants take up nutrients as their inorganic form. In the case of P according to literature this is ...
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How cells determine how many enzymes are needed for digestion

How do pancreatic cells, epithelial cells of the stomach and intestinal epithelium cells determine the right amount of enzymes for digesting carbohydrates, proteins, fats? How does the pancreas ...
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Question about vitamin b6 product and cycling

Can the b6-product of a vitamin b6 reaction such as transaminase be recycled back to active vitamin b6 in man, and if so by means of what reaction?
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Is egg white lysozyme different from bacterial lysozyme?

Someone told me that microbial lysozyme has effect on gram negative bacteria but egg white lysozyme only affect gram positive bacteria. Is it true?
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Acute calculous cholecystitis

The action of mucosal phospholipases hydrolyzes luminal lecithins to toxic lysolecithins. The normally protective glycoprotein mucus layer is disrupted, exposing the mucosal epithelium to the direct ...
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Molecular Docking Enzyme Inhibitor Biosensor?

I had some task to study Molecular Docking relations with Biosensor and I am really new with this discipline (beginner). I am docking C60 with Glucose Oxidase and my question is: what would happen if ...
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Why don't phosphatases both add and remove phosphate groups if enzymes catalyze reactions in both directions?

We know that Phosphatase is a type of enzymes that removes a phosphate group. Why can't phosphatases add a phosphate group if we know that all enzymes reactions are reversible ?
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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 ...
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How can enzymes be immobilised on glass?

I’m studying a hypothetical model for urease activity, which involves fluorescence measurement, hence the need for an optical window to which the enzyme urease is immobilised. From my previous ...
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How do I confirm TycA (3'-N-debenzoyl-2'-deoxytaxol N-benzoyltransferase) activity?

I know the TycA enzyme catalyses the following reaction: N-debenzoyl-(3'-RS)-taxol + benzoyl-CoA → taxol + coenzyme A + H+ But I don't know how to confirm its activity. I have confirmed protein ...
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Why is it more difficult to measure a decrease in fluorescence in FRET assays?

In the slides, the professor mentions that it is better to use a substrate double labelled with donor-acceptor molecules because we start with FRET quenching and measure increase in fluorescence if ...
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Can experiments in ELISA kits be monitored via both fluorometry and photometry?

In my bioanalytics course slides, the professor has written at one point that in a heterogenous immunoassay such as ELISA, we use fluorimetry to measure concentration of an analyte. In another slide ...
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What does “operationally soluble” mean, re. Tax10 enzyme?

I am trying to work out whether the enzyme Tax10 is soluble or insoluble. I need to know if some buffers won't work with Tax10. I am trying to confirm Tax10 activity, having confirmed protein ...
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1answer
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How do metal ions acting as enzyme cofactors “find” their respective enzymes?

Metalloproteins are metal-dependent proteins, i.e. they require certain metal ions (copper, magnesium, zinc, etc.) for their correct function in the body. Since proteins are manufactured inside cells ...
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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 ...
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What options exist to quantitatively detect enzyme activity in non-model insect tissue?

Evolution/genomics person here: what are the options to measure the activity or presence of broad categories of enzymes--like peroxidases or catalases--active in a specific tissue (in a non-model ...
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Why is pepsin able to operate at low pH?

Pepsin is a protease that operates in the acid pH of the stomach. Many proteins are denatured at low pH, and most enzymes — whether or not they denature — require a higher pH for activity. Why is ...
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Is this experiment to check enzyme reaction rate according to substrate concentration correct?

We just had an experiment to check enzyme reaction rate according to it's substrate concentration. In the experiment, we used a varying amount of substrate and the same amount of enzyme: (1.5mm enz, ...
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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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Looking for references on protein activity prediction

My colleagues have measured Kcat for 29 mutants of a certain enzyme and they've studied the possible impact of those mutations on the protein's physicochemical properties through computational models. ...
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271 views

How does one calculate [Et] (total enzyme concentration) in enzyme kinetics using Vmax?

I'm trying to work out a question where I have to calculate the Kcat of an enzyme-catalysed reaction. I've read that Kcat= Vmax/[Et]. I have worked out Vmax using a Lineweaver-Burk plot, which is 8.3 ...
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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! What does pH of 14 look like? [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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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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1answer
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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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Transaldolase vs Transketolase

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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Comparison between banana and human dopa oxidase

Dopa oxidase - an enzyme which catalyses the conversion of L-dopa to dopachrome - can be extracted from bananas but is also present in the mamilliam brain as a precursor to a number of ...
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1answer
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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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Non-Competitive Inhibition vs Allosteric Inhibition

The Vmax of a reaction is lowered in presence of a non-competitive inhibitor (compared to the control - without a inhibitor) However, (Vmax of the reaction stays the same in presence of an allosteric ...
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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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1answer
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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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98 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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The term when enzyme is “deformed”? [duplicate]

I am researching on the effect of hydrogen ions concentration (ph) on the rate of activity of enzymes. I currently understand that the hydrogen ion is charged and therefore would affect the ...
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1answer
147 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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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?