Working principle of enzymes
Posted 18 February 2012 - 10:06 AM
I havent had a lot of courses in biochemistry/enzymekinetics and I am struggling with a few things about enzymes.
For example on the wikipedia article about enzymes they mentions the following: "Enzymes catalyze the forward and backward reactions equally." What does this mean?
I checked it and I (seem) to understand the example (carbonic anhydrase, should catalyse both reactions), but does it mean that every enzyme catalyses both the forward and backward reactions? Or not all enzymes?
I am getting a bit confused because I learned that often: A => B (done by enzyme X) while B => A is done by another enzyme.
So does it just depend on the specific reaction?
And what with for example this: http://en.wikipedia....:Glycolysis.svg , you see some <=> in the shedule, does a <=> mean that both => and <= are catalysed by the same enzyme? Or does it mean that an enzyme can catalyse => and that <= can happen spontanously? (or maybe that both => and <= are catalysed by the same enzyme?)
Thanks in advance.
Posted 18 February 2012 - 12:21 PM
Posted 18 February 2012 - 02:32 PM
The Gassy Vet
Posted 18 February 2012 - 04:38 PM
From a quick search, it seems that the problem with alliinase is that the protein produced by the gene is further processed by some (perhaps unknown) mechanism, that makes it unviable to just produce it from cloned genes. I don't know it there is likely to be any easy/cheap way of extracting it in bulk from garlic or onions.
If you follow some of the links in the tables on the right hand side of the wikipedia page for alliinase, there are some papers on there that should be more helpful in gaining knowledge about the problems than I can be.
Posted 19 February 2012 - 01:29 AM
Enzymes (and catalysis in general) can only make reactions which would happen anyway happen faster, often dramatically faster. Every reaction is reversible, in principle. But reality can intrude. Cells may have very high concentrations of reactant A and little of B, so that the reaction A->B occurs preferentially. Some reaction products can be removed (i.e. it is a gas, or precipitates, or is the substrate for a subsequent reaction) making the reverse reaction rare. You need to understand equilibria and the role of concentrations in driving the equilibrium of reactions.
The problem I had, was that often they only refer to an enzyme as being a catalyst for just 1 reaction.. and I only found a few enzymes where they mentioned that it can also catalyse the opposite reaction.
While I learned in the past that a catalyst (in theory) should catalyst both reactions...
So I got confused about it, especially since they also started to mention that for some "reversible" reactions 2 different kinds of enzymes were used to catalyse the forward/backwards reactions.
Posted 21 February 2012 - 12:05 PM
[url="http://www.worthington-biochem.com/introBiochem/default.html"]worthington introduction to enzymes[/url]
i'm also attaching a pdf of the site in case you can't access it.
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