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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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 ...
17
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300 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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328 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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2answers
691 views

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 ...
13
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1answer
6k 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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2answers
626 views

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 ...
10
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1answer
811 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 ...
10
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372 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 ...
9
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1answer
186 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 ...
8
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1answer
405 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?
7
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2answers
388 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 ...
7
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1answer
189 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 ...
6
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2answers
611 views

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. ...
6
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1answer
82 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 ...
6
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1answer
156 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 ...
6
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3answers
130 views

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 ...
6
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1answer
265 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?
6
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2answers
62 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. ...
5
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1answer
899 views

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 ...
5
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2answers
420 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 ...
5
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1answer
386 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 ...
5
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1answer
275 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?
5
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1answer
76 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 ...
5
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1answer
318 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 ...
4
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1answer
495 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 ...
4
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1answer
92 views

Causes of monozygotic twins

Twins could be monzygotic i.e. identical twins and dizygotic i.e. non-identical twins.Well, monozygotic twins occur when a single egg is fertilized to form a zygote which later divide into separate ...
4
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1answer
74 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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292 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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1answer
100 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 ...
4
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1answer
23 views

Telomerase in tetrahymena

In this amazing video, at 26:03 we see this image We now know that the telomerase contains a sequence complementary to the telomere sequence and so is able to do what it is capable of doing in this ...
4
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0answers
156 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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0answers
49 views

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, ...
3
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3answers
74 views

What does “kcal/mol” mean when speaking of enzyme catalysis?

After thinking about it, I'm confused by what the reaction barrier of an enzyme actually means. Imagine a reactor containing enzyme and substrate. If the enzyme in the reactor has a reaction barrier ...
3
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1answer
171 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' ...
3
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1answer
33 views

Literature about industrial enzyme application

Can someone point me out to literature (reviews or better workbooks) describing industrial chemical reactions catalysed by enzymes? What I'm most interested in are case studies of how the output of a ...
3
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1answer
35 views

What happen's to a virus's capsid after it injects its genetic material into the host cell?

After a virus (one of the varieties which infects the cell via injection and not endocytosis) injects its genetic material into the host cell, what happens to it's protein coat? I would guess that it ...
3
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3answers
100 views

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.
3
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0answers
30 views

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 ...
3
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0answers
25 views

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 ...
2
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3answers
53 views

The effect of pH on enzymes

I am currently studying biology and have a question. I know that as pH increases, enzyme activity increase until the enzyme's optimum pH is reached. However, I would like to know why as pH increases ...
2
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3answers
417 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. ...
2
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1answer
26 views

What stops telomerase?

The telomerase is an enzyme that adds telomeres. What stops the telomerase from adding too many telomere sequences ? What's the regulating mechanism ?
2
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2answers
89 views

Are there enzymes found in nature or the man made world that can help break down metals?

The title says it all. Do natural or human engineered enzymes exist that can speed up the break down kitchen utensils, aluminum cans, wires, etc. into small particles or powders? To be clear I am ...
2
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1answer
30 views

Activity of glucokinase

From Solomon et al, 2013 ACC Synthetic biology and from this video : Here, there are 2 competing reactions for glucose - one with glk as enzyme and other with gdh as enzyme. In the graph, y axis ...
2
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1answer
71 views

Determining sequence of oligoribonucleotide

Oligoribonucleotide X was treated with phosphatase (for removal of 3' and 5' - terminal phosphates), then with RNAase T1, which cleaves all phosphodiester bonds located in a 3' position of ...
2
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1answer
55 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)
2
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1answer
30 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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1answer
16 views

2 types of telomerases?

As telomerase works by adding new nucleotides complementary to the RNA it contains, it cannot work for the complementary strand. Say telomerase X has RNA complementary to the 5' to 3' strand it ...
1
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1answer
59 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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1answer
16 views

Correlating Ki values of pesticides to bacterial growth

Four pesticides P1 to P4 are reversible inhibitors of an enzyme E that is essential for the growth of a bacterium B. Their Ki values are given in the table below. Each of these four pesticides ...