MrDarwin

I can tell already that the creationists are going to love this one:

Without Enzyme Catalyst, Slowest Known Biological Reaction Takes 1 Trillion Years

GunnerJ

Say, how the hell do enzymes work, anyway?

Deadbeat

So the god of the gaps has just become god of the enzymes?

*sigh*

I see what you mean, MrD. I can already imagine the logical fallacies and twisted reasoning to which this will give birth.

NonHomogenized

dammit. This means I'm now going to have to explain the concept (and origin. and method of functioning) of enzymes to stupid bastards (read as: creationists) when I'm explaining to them in nice, small words, what the theory (and fact) of evolution is, and why it works.

*sigh* [grabs nutrition 251 textbook, and google.]

Kosmo

Funny topic,
One almost cringes reading the title of an article like that, it seems innocent enough yet you know it's inevitable that this will soon appear in some 'scientific proofs against evolution' list.

Of course, if one mixed a couple moles of hydrogen with a mole of oxygen in a balloon, it'd take 5 times the life of the universe to get any appreciable amount of water... unless there was a spark.

lpetrich

It's 2 of hydrogen + 1 of oxygen; 2 volumes of hydrogen + 1 of oxygen at constant pressure.

As to the room-temperature reaction rate, it will be very sensitive to temperature:

r ~ r0*exp(-E/(kT))

where E is the activation energy. The hydrogen and oxygen atoms have to go into some more-energetic configurations before they can reach the water-molecule arrangement.

A catalyst is a substance that can speed up chemical reactions. Platinum will speed up hydrogen + oxygen -> water by making hydrogen and oxygen molecules stick to it ("adsorption"), thus lowering the intermediate-energy "hump".

However, a catalyst does not change a reaction's thermodynamics; platinum can break water up into hydrogen and oxygen, but that is so energetically unfavorable that that reaction is VERY slow.

As to GunnerJ's question, an enzyme is a biomolecule catalyst; it works in essentially the way that platinum works with hydrogen and oxygen, by making other molecules stick to it so they can react more easily.

Enzymes have the nice property that they are often very specific; only molecules with specific shapes, subgroups, etc. will stick to them.

theyeti

They lower the activation energy of a reaction.

Any reaction catalyzed by an enzyme must have a negative (delta)G (i.e., be spontaneous). They cannot make a non-spontaneous reaction become spontaneous, although they can couple a non-spontaneous reaction to one which is spontaneous; as long as the net (delta)G is negative, it'll run in the forward direction. But many reactions require some input of energy before they can run, which is called the activation energy. If you're burning gasoline, for example, you have to have a spark before the reaction will proceed, even though it's obviously a highly spontaneous reaction. Enzymes lower the amount of that energy needed to make the reaction run. If you had an enzyme which lowered the activation enegy for gasoline combustion, it would mean that you could use a smaller spark, or perhaps room temperature would be sufficient.

A good analogy is to imagine an elevated lake held back by an earthen dam. You need energy to raise the water above the dam before it can run downhill and result in a net production of kinetic energy. But if you lower the earthen dam, the amount of energy required is less and the "reaction" can happen more easily. But the net kinetic energy remains the same regardless. Enzymes typically acomplish this by binding and stabilizing high energy intermediate states which would not tend to hang around for very long otherwise.

theyeti

Albion

Enzymes work in two different ways (that I remember from chemistry classes, anyway). There are the purely physical ones, which provide a surface which holds the reagents at the optimal distance and configuration for undergoing a reaction that wouldn't occur if the reagents were just wandering around in solution, and there are the chemical catalysts, which are involved in the reaction itself but are regenerated during the reaction, so that they're still around afterwards to carry on catalysing. I think the early catalysts in the production of complex organics are thought to be of the first sort - clays and minerals at the coastline or at deep-sea vents that concentrated the simpler organic chemicals on their surfaces and made reactions more likely simply because the reagents were brought into frequent contact with each other. Later catalysts, including the self-catalytic RNAs, could have been the latter sort, once the complex organics had been formed in the first place.

burning

Looks like instead of trying to discover the origin of life people should have been trying to discover the origin of enzymes. Anybody try figuring out the probability of this happening on purpose vs. by accident...before the creationists do?

-Say, there's a discussion about aliens planting life on earth on another thread...

Wounded King

Do you want to know about enzymes in trems of protein specifically Burning, because I just read a really interesting paper on ribozymes. It covered a technique I hadnt come across before called selex (Systematic Evolution of Ligands by EXponential enrichment) which allows the development of Ribozymes for a specific reaction. It is most easily done in terms of catalysis by simply providing a substrate to hold the reactants in close proximity. You merely screen a large 1X10^17 library of RNA molecules for binding affinity to your reactant and then PCR up strands that bind. You then repeat the process, adding some random mutations to provide variation. After several rounds of this you, ideally, come out with a high affinity Aptamer.

This is admittedly not strictly Enzyme evolution but it does show that a catalytically active biological molecule can evolve, so I dont see why the process should be significantly different for proteins. Obviously in the in vivo situation the selection is based on how the binding property of the protein/ribozyme aids the fitness of its host higher affinity binding leading to increased fitness leading to more copies of that gene being extant.

I cant find the paper on pubmed, it seems to hate things from Biologist. Here are some related links though

Gold L, Brown D, He Y, Shtatland T, Singer BS, Wu Y.
From oligonucleotide shapes to genomic SELEX: novel biological regulatory loops.
Proc Natl Acad Sci U S A. 1997 Jan 7;94(1):59-64.
http://www.pnas.org/cgi/content/full/94/1/59

and an in vivo example

Ayre BG, Kohler U, Turgeon R, Haseloff J.
Optimization of trans-splicing ribozyme efficiency and specificity by in vivo genetic selection.
Nucleic Acids Res. 2002 Dec 15;30(24):e141.
http://nar.oupjournals.org/cgi/content/full/30/24/e141