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8

all 10 steps in glycolysis require an enzyme We count it as 10 steps because there are 10 enzymes. There might be other steps that are fast (like a product acting as an acid or base) that we don't count because they don't need an enzyme. I’d have thought that evolution would have selected for “simpler” pathways. What is simple is that everything is ...


6

Enzymes act as catalysts to increase the rate of reactions. In the absence of enzymes, most biological reactions would be incredibly slow, in some cases many many orders of magnitude slower than when catalyzed. Given the large number of biological reactions that require enzymes, it seems that there might be an advantage to reactions that are slow in the ...


5

We speak of reactions that build complex molecules or break complex molecules at a specific position they must happen at constant 37°C all of which must be rather low energy or be very well controlled, like photosynthesis no fancy other reagents are available many would never happen at all without stringent control and/or the result could only be achieved ...


5

The authors mention three residues that they consider "second shell", 12, 77, and 102. They are shown in the figure below in green: Residues Trp50 and Glu101 are directly involved in ligand binding, shown as space-filling in yellow. As you can see, they are part of the central beta barrel. The residues in green are also part of the beta barrel, but the side ...


5

I think I got it. The diagram in PubChem is not bromelain molecule, but a tiny fragment of it. This thing is indeed too small to be an enzyme. Also, it has nothing to do with proteins. Look at the formula, there is not a single amino acid residue here. Indeed, scroll down to 3.4.2 and read: "carbohydrate moiety of bromelain". That's what it is, and not the ...


3

I was forced to look at the wikipedia entry for enzyme, which states: Enzymes /ˈɛnzaɪmz/ are macromolecular biological catalysts that accelerate chemical reactions. [...] Most enzymes are proteins, although a few are catalytic RNA molecules. The latter are called ribozymes. [Enzymes' specificity comes from their unique three-dimensional structures.] The ...


3

Acetylcholinesterase is important enzyme and its mechanism of function is well known. In active site, it has two pockets: anionic pocket (to attract positively charged Quaternary nitrogen of choline) and esteric pocket. The esteric pocket consists of a serine side chain (a $\ce{-CH2-OH}$ function) as depicted in following cartoon, which pacilitate the ...


3

There is a recent crystal structure of a bromelain precursor protein. PDB Entry 6U7D http://www.rcsb.org/structure/6U7D Usually "precursor" means that the active form of the protein is formed by cleaving off a piece or pieces. I do not know if that is the case for this protein. However the protein used to grow these crystals was expressed in E. coli, so ...


2

Until the late 2010s, it was considered impossible to reactivate acetylcholinesterase that has undergone aging. However, in recent years, new advancements have been made that show promise in this area. A group of researchers investigated several sulfonium-containing alkylating agents that were supposed to alkylate the phosphonate moiety bound to the serine ...


2

Life is all about a little compartment controlling the (bio-) chemistry inside it. From the moment the first cellular predecessors started forming in whatever the medium they had was, they had an ‘inside’ and an ‘outside’ and life evolved by taking control of the ‘inside’, protecting it against the ‘outside’ and then by some means, propagating the ‘inside’ ...


2

If the substrate still binds to the protein, other parts of the mechanism are still in place. Specifically, the main chain amide groups that help to stabilize the tetrahedral intermediate are still present. In the absence of serine, water will attack the carbonyl. In the presence of serine and the absence of the histidine, serine will still be the ...


1

Matthew's answer corrected some mistakes which I have made in asking my question. His answer also suggests that OP compounds that contain hydroxyl groups would indeed cause instant aging of inhibited cholinesterase. I have found confirmation that that is indeed the case. There is a naturally-occurring organophosphate that contains a hydroxyl group, formerly ...


1

What is the definition of a “Simple enzyme” exactly? This is not a term that is commonly used. There are commonly used terms for an enzyme lacking its cofactor (apoenzyme) and having its cofactor (holoenzyme). Also, the term "enzyme complex" is used for the enzyme bound (non-covalently) to other molecules. Does this mean that any protein that utilizes a ...


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