Enzymes are globular proteins that catalyze 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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Adenosine metabolism

Are adenosine or its catabolites increased in inflamed airways? How can I assess this? I am trying to use inhibitors for adenosine deaminase, xanthine oxidase, and purine nucleoside phosphorylase, but ...
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165 views

Function of papain in papaya

I know that papain is a proteolytic enzyme present in papaya. It is often used to tenderise meat. What is the function of papain in papaya? Is papain sweet? Does it function as an antibiotic?
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125 views

Creative ways to deactivate alpha-amylase taken from fungi

I can deactivate $\alpha$-amylase in ways such as extreme temperature controls, pH controls of the solution it stays in, or adding salt to the solution. However, are there any other unique or ...
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2k views

Renin - enzyme or hormone?

Wikipedia says : The kidneys secrete a variety of hormones, including erythropoietin, and the enzyme renin. Can a substance be both an enzyme and a hormone ? Why is renin both an enzyme and a ...
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Are there any enzymes synthesised by humans that specifically catalyse the hydrolysis of non-cyclic Imides?

Imides or dicarbonyl amides are an interesting class of compounds that includes the pharmaceuticals thalidomide, aniracetam and a few other drugs. These compounds, however, are cyclic and I'm ...
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Why are diabetic people often overweight?

I was looking at diabetes the other day, and I noticed something strange. Lower amounts of lipase are a symptom of diabetes, as is overweightness. However, since lipase is the enzyme that breaks down ...
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Are there any methods to quantify H2O2 (hydrogen peroxide) which don't rely on horseradish peroxidase?

I can't use HRP since my substrates interfere with it and I need a real-time method because I want to measure kinetic parameters of some oxidases.
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60 views

Carotenoid biosynthesis in yeast

Does Budding Yeast Sacchromyces cerevisiae produces significant amount of carotenoids? Have anybody estimated the ratio of flux going in branches 1. Cholesterol synthesis(via squalene) 2. Coenzyme Q6 ...
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2answers
493 views

Why are enzyme-catalysed reactions slower at lower substrate concentration?

Suppose I'm using 200 nmoles of enzyme and 2 mmoles of substrate. The enzyme should be saturated but if I use 50 mmoles of substrate, the reaction will be faster. Why? I just can't get it! Even at ...
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93 views

Photosynthesis regulation

I read about the regulation of Calvin cycle by thioredoxin which activates key enzymes essentially by converting disulphide linkages on inactive enzymes into sulfhydryls. Another regulatory mechanism ...
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984 views

Michaelis-Menten Kinetics: Does measuring apparent Km and Vmax take into account competing reactions?

I am learning about why it is important to measure Km and Vmax for each experimental setup because measuring the "apparent" Km and Vmax includes enzyme inhibitions of which one might not be aware. ...
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457 views

What is the biological mechanism underlying caffeine intolerance? (CYP1A2 or other?)

As far as I can tell, caffeine metabolism occurs primarily via the CYP1A2 enzyme. I am curious as to whether mutations in the CYP1A2 gene are associated with caffeine intolerance. Some site that is ...
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92 views

Cereal Alpha and Beta Amylase temperature range and reaction rate

This question is motivated by a practical application in bread making. While it is well known which are the optimal (highest reaction rate) temperatures for both alpha and beta amylase, I am not able ...
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1answer
46 views

Does the Enzyme Monoamine Oxidase, Isoenzyme A have an allosteric modulatory site?

Does the Enzyme Monoamine Oxidase, Isoenzyme A (MAO-A) have an allosteric modulatory site? I ask because I would like to know if it is possible, in theory at least, for a positive allosteric modulator ...
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114 views

Specific enzyme for C. elegans [closed]

We are looking for an enzyme that appears in C. elegans but isn't common for: human, Drosophila or mouse. We need it for a little research project, thanks for your help!
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28 views

Which Enzymes Degrade Dynorphins and what drugs are there available to inhibit said enzymes?

Which Enzymes Degrade Dynorphins and what drugs are there available to inhibit said enzymes?
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61 views

Which Enzymes are Responsible for the Biodegradation of Noladin Ether?

Which enzymes degrade the CB1-specific endogenous cannabinoid 2-arachidonyl glyceryl ether? (Noladin ether)
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1answer
48 views

Which Enzymes are Responsible for the Biodegradation of Beta-endorphin?

Which enzymes are responsible for the biodegradation of the endogenous opioid peptide, beta-endorphin?
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376 views

Questions regarding ELISA

I have recently peformed an ELISA (Enzyme-linked immunosorbent assay), but I still have some questions, let me first outline what I did: We had a number (20) of tubes containing fake 'bodily fluids' ...
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1answer
767 views

How are lysosome membranes protected from the attack of hydrolases?

Lysosomes are a bit like the suicidal bags of cells. They help to clean cells, have an acidic pH and contain a large number of hydrolyzing enzymes. But why don't these hydrolyzing enzymes attack ...
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494 views

$S_{0.5}$ vs $K_m$ values in enzyme kinetics

What is the difference between $S_{0.5}$ values and $K_m$ values in enzyme kinetics?
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129 views

Are there any websites offering graphs for the light absorption of different enzymes?

I have found graphs for the light absorption of water, haemoglobin, lipids, melanin, etc., but I am having a hard time finding graphs about enzymes. Are there any websites or other reference sources ...
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2answers
69 views

Predicting and identifying microbes and enzymes DNA sequence with metabolic prediction

Presently I am working on metagenomics of coal biomethenation by bacterial consortium. I have got the sequence result (Illumina). The sequence is huge and I can't predict anything from the sequence. ...
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408 views

What are the units of enzyme activity?

I was looking at this graph of turnip peroxidase activity and I saw that they use units of 1/sec for enzyme activity. What does this unit intuitively represent and how is it calculated?
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Is the EC50 of an activating protein for an enzyme a good indicator for the binding affinity Kd?

We work with a membrane protein system where measuring the affinity between the enzyme and the upstream activating protein has been difficult, and when measured in detergent solution, it is almost 100 ...
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1answer
828 views

When is the lactase in lactose-free milk active?

Recently we have started suspecting that one of our children has hypolactasia (lactose intolerance), and so accordingly I have had my first exposure to lactose-free dairy- and dairy-like products. In ...
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290 views

How do the pharmacodynamics of the NSAIDs differ and are there “resistant” COX phenotypes?

I know that the non-steroidal anti-inflammatory drugs (e.g., aspirin, ibuprofen, naproxen) affect the enzymes cyclooxygenase (types I and II). Is there any difference in the degree to which these ...
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Is it possible to repopulate lactase in the stomach? [duplicate]

Possible Duplicate: Can an adult without genetic lactase persistence still develop a tolerance for dairy foods? In my younger years, I don't seem to have a problem drinking milk. Nowadays, ...
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What is the correct model for enzyme-substrate complementarity?

This Wikibook shows both proposed models of enzyme-substrate complementarity, the Lock and Key model and the Induced Fit model. I've always been taught that the Induced Fit model is the proper one. ...
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494 views

How fast does the rotor in ATP synthase spin?

I'm sure the exact frequency varies, but does anyone know roughly how many revolutions per minute / second the rotating center part makes?
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596 views

What conditions are necessary for HPL (human pancreatic lipase) to activate?

What conditions are necessary for human pancreatic lipase to activate? Is there an optimal temperature or pH? How quickly does it take effect?
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1answer
90 views

Is there a tool to find the action of an enzyme in a metabolic pathway?

Is there any tool to search the biochemical action of a particular enzyme in a metabolic pathway of an organism? In other words, how can I find if enzyme "E" is involved in the metabolic pathway for ...
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209 views

Is there an enzyme for the transformation of the hydroxyl group?

I would like to know, is there any enzyme which does the transformation of hydroxyl group to any other functional group using the enzyme. The substrate is aromatic hydroxyl group. Product should not ...
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230 views

Compare and contrast “Rubisco activity” and “assimilation rate” (is there a difference, and if so, what is it)?

I am confused about the variable "RuBisCO activity". How is it measured, and is it any different from the net assimilation rate? Based on some background reading (e.g. Kling, 2008; Lambers et al ...
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How crowded is the bacterial cell?

I was wondering what is the protein concentration in an E. coli cell. When studying enzyme kinetics and activity in vitro, I would argue that the substrate and enzyme concentrations resemble those in ...
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453 views

Why does cyanide inhibit CuZnSOD, but not MnSOD or FeSOD?

Different types of superoxide dismutase (SOD) contain different metal ions (Zn, Cu, Mn, Ni, or Fe), all of which allow them to catalyze one reaction, dismutation of superoxide anion, O2−. Cyanide can ...
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How does the enzyme ATP Synthase use a proton concentration gradient to make ATP?

I understand what the enzyme ATP synthase does, but I'm not exactly sure how it does it. I've heard that it uses rotary catalysis, but how exactly does this work? How is the energy from the H+ ion ...
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1answer
11k views

What effect has changing pH and salt concentration on protein complexes?

I'm struggling to find peer reviewed literature that explains the effect of changing the pH and the salt concentration on protein/protein complexes in solution. What effect does the pH and the salt ...
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Why are restriction enzymes not frozen?

We all know restriction enzymes are proteins, but we never freeze them. They are instead provided in high glycerol containing solutions by companies and stored at -20C. Is there a reason why this is ...
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606 views

How can I measure bacterial alkaline phosphatase activity?

I want to measure alkaline phosphatase activity using PNPP in my mutant bacteria strains, but all the protocols I found involve purification of the phosphatase (which I have no need of). Does anyone ...
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193 views

What are the clotting factors' effect on avascular necrosis development?

Do clotting factors tpa and pai-1 lead to degenerative osteoarthritis in the same way that lupus anticoagulant and prothrombin might? Is one of these pathways particularly detrimental during formation ...
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341 views

Can an adult without genetic lactase persistence still develop a tolerance for dairy foods?

While investigating the rise of adult lactose tolerance, I came across the news that China has been encouraging its citizens to drink more milk, even though most of the Asian population lacks the SNP ...
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1k views

How is Taq polymerase produced?

I've seen Taq polymerase being marketed as either "native" or "recombinant". I understand that the recombinant version is produced by specially modified Escherichia coli strains that have the gene for ...