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15

According to "Resolution of distinct rotational substeps by submillisecond kinetic analysis of F1-ATPase" (Yasuda et al., Nature, 2001), ATPase rotates at 130 revolutions per second when saturated with ATP.


15

It seems that yes, it is possible to increase the tolerance for lactose over time, and it has to do with the adaptation of microbiota. A simplistic explanation comes in the following article: Hertzler SR, Savaiano DA. 1996. Colonic adaptation to daily lactose feeding in lactose maldigesters reduces lactose intolerance. The American journal of clinical ...


13

The formation of protein complexes or aggregates in aqueous buffers is determined by a number of factors: physical properties of the protein itself, pH, temperature, type and concentration of the used cosolvent (salt). Solutes are often roughly divided by type into chaotropes ('disorder-making'), which destabilise protein structures and kosmotropes ...


12

It's just so much more convenient to have the enzymes ready without having to thaw them. The main reason you freeze enzymes is to keep them active, if you figure out a buffer that keeps them unfrozen without compromising activity, that is a huge increase in convenience. Not having to thaw the enzymes before use saves a lot of time, if you can manage to keep ...


9

You can certainly get massive differences between EC50 and affinity. This is especially true for cell-based assays and membrane protein systems. The reason why is because the appropriate time scales to achieve binding equilibrium (hrs for nM affinity, days for picomolar, feptomolar affinity according to back of the envelope calculations) may be and likely ...


8

This is true of all protein binding as well as the special case of enzyme-substrate interaction: Various proteins are more dynamic than others: some have only one or two overall conformations and are relatively implastic otherwise. An example would be a receptor tyrosine kinase like Kit (or CD117, or Mast Stem Cell Growth Factor Receptor, whatever you want ...


8

The macromolecule concentration within E Coli is estimated to be around 0.3-0.4 g/ml [1] The concentrations of your substrate in respect to your enzyme are generally fairly analogous to in vitro studies compared to in vivo studies. However, this is heavily based on the assumption that the diffusion constants for both molecules stay consistent. In many cases ...


8

I think the KEGG pathway database may be of some use to you. Link is here: http://www.genome.jp/kegg/pathway.html This a database of manually drawn pathway maps, I have used the site myself and it is very useful in determining if your enzyme is in a pathway and where it lies in it. This is assuming though, your enzyme is in the database and has been ...


8

Image from wikipedia page on ATP synthase In brief, the addition and release of protons to the structure cause a conformational change that leads to another conformational change. This series of conformational changes occurs in such a way that it induces a rotational motion. The rotation of the central axel that extends through both hemispheres of ...


7

First of all we should distinguish between the physiological clotting factors that are parts of the normal clotting pathways, and those that might affect clotting pathways but are not observed under healthy conditions. TPA (tissue plasminogen activation), PAI-1 (plasminogen activator inhibitor) and prothrombin are normal clotting factors that are essential ...


7

It is possible to search for enzymes or a series of enzymes that will take similar reactants to similar products. ReBIT allows you to query enzymes by your molecular structures of interest using their SMILES code. Unfortunately, a quick search using coumarin didn't produce any results but searches for phenol and phenolate gave some hits. If you're seeking ...


6

In what follows I am going to attempt to answer your question using a specific example of (competitive) reversible activation, and I hope to show what a misleading parameter EC50 can be. (Rate law derivation is an area of interest, hence the long-winded answer). It can of course give information, but IMO it needs to be used with extreme care. I am ...


6

Having done an inordinate number of rather mind-numbing A.S. practicals involving milk and enzymes the year before last, in my experience lactase always began breaking down the lactose immediately and converting a boiling tube worth of milk in less than 50 minutes at below room temperature. To further allay your concerns, this website suggests that most ...


6

Composition of E. coli (dry weight): 55% protein, 20% RNA, 10% lipid, 15% other Protein concentration is about 100 mg/ml or 3 mM. From the size of an E. coli cell, 1 nM is about 1 molecule/cell. This is ~1000 molecules/cell for HeLa cells. Diffusion coefficient for an "average" protein: D ~ 5-15 microns^2/s, or ~10 ms to traverse an E. coli. For reference, ...


6

For a great visualization of the macromolecules inside the cell, check out David Goodsell's illustrations. He tries to reproduce the protein and DNA density within the cell to show how things might be in vivo. Really great stuff. The answer is - its very concentrated. Compare the density of the cell to that of a typical crystallized protein, which is I ...


6

The protein referred to in the question is encoded by gene PNLIP, pancreatic lipase. From this annotation of the protein, I see that there is a signal peptide from amino acids 1 to 16. Thus, this signal peptide must be cleaved before the protein can be active in its digestion of emulsified triacylglyerides. A paper describes the structural changes induced ...


6

How are diabetes and obesity connected in light of low lipase activity? Short answer: There's more than one type of diabetes. (And to complicate things, there's also more than one type of lipase. It's unclear from the question which type were mentioned in what you read.) Diabetes mellitus is usually divided into Type 1 (insulin-deficient) and Type 2 ...


6

Yes, something can be both a hormone and an enzyme. There are a group of hormones known as peptide hormones. These are proteins (such as enzymes) that act as hormones indirectly (and maybe directly too?). A hormone is a chemical secreted by a cell that has some effect on another cell elsewhere in the body. In this case, the chemical just happens to be an ...


5

Freeze-thaw cycles denature proteins through local pH change effects


5

Here are my thoughts on the topic. Dairy good is not only milk, but also the following milk products: sour milk products (like yougurt, kefir, katik, buttermilk, etc.), cheese, etc. These products can contain less lactose than in the milk solids (due to fermentation during processing). It is also common for some of these products to contain living ...


5

This refers to the turnover number (a.k.a kcat or k2) of an enzyme and is usually calculated using Michaelis-Menten kinetics. Jump to the summary at the end if you want a simple answer. If you want a more thorough answer, consider the following chemical equation: [E] + [S] ⇌ [ES] → [E] + [P] This says that a certain concentration of enzyme mixed with a ...


5

Early histochemical work indicated that the internal surface of the lysosomal membrane has a glycocalyx - a layer of polysaccharide, presumed to have a protective role. Neiss, W. F. (1984) A coat of glycoconjugates on the inner surface of the lysosomal membrane in the rat kidney. Histochemistry 80, 603–608 Subsequently it was found that major membrane ...


4

Both models are true depending on how you frame the mechanisms of catalysis. As mentioned by @Blues, proteins are highly dynamic. In that manner, a protein will adopt both the unbound active state shown in the induced fit model and the complementary shape shown in the lock and key model. (apologies since this is the only figure that I could find to explain ...


4

For recombinant Taq polymerase, industrial-scale production produces liters of highly concentrated enzyme in a single run. It comes in such small, dilute quantities when sold that only a few preps a year would be necessary to satisfy research lab demand. I don't know the Thermus aquaticus protocol, but considering the achievements in yield for E. coli, and ...


4

Your question conflates two separable events, a redox process and an acid-base dissociation. The interconversion between disulfides and free sulfhydryls is a redox reaction, governed by the redox potential of the surroundings. The importance of redox potential to the -S-S- <> -SH equilibrium is illustrated by the difference between the cytosol and the ...


4

A few possible explanations are named in the Wikipedia article you link: Regarding spontaneous or natural monozygotic twinning, a recent theory posits that monozygotic twins are formed after a blastocyst essentially collapses, splitting the progenitor cells (those that contain the body's fundamental genetic material) in half, leaving the same ...


4

In the β-lactamase test, an inhibitor of β-lactamase is added to a sample of the culture medium. The inhibitor binds to the enzyme and changes its color, which is in direct correlation to the concentration of the β-lactamase. More β-lactamase means more inhibitor binding and this results in more color development leading to a higher ...


4

Enzymes have a more or less narrow optimal pH at which they work, depending on the conditions of their environment. Pepsin for example is active in the stomach which is pretty acidic and has an optimal pH of 2.0, while Trypsin, which is active in the small intestine has an optimal pH around 8.5. Changes in the pH first affect the form of the protein, ...


4

In human cells it takes about 20 s to make a 20,000 dalton enzyme. Assuming that the cells concerned are already making mRNA for the enzyme, there will be two main factors: (1) The time taken to synthesize the polypeptide (2) Any time taken to fold the protein (If the enzyme is secreted from the cell there will also be the time taken for the protein to ...


3

There's a paper from 1973 describing a very simple protocol: Wolf PL, Von der Muehll E, Praisler K. 1973. A test for bacterial alkaline phosphatase: use in rapid identification of Serratia organisms. Clinical chemistry 19: 1248–9.



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