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Society for the Study of the Origin of Life


The role of peptides in the origin of life
Christian de Duve Scientist
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Peptides... amino acids, of course, were present among the bricks of life, so there's no difficulty, and joining amino acids into peptides is a relatively simple... I wouldn't say it's simple, but it's something that could have occurred. A number of mechanisms can be proposed and, in fact, there is even evidence that the cosmic chemistry makes peptides. There is evidence that peptides... dipeptides, at least, are present on meteorites and there is evidence that peptides may form, under laboratory conditions, mimicking the conditions in outer space, very low temperature, very high vacuum and radiation. So if... peptides have been made by a Japanese group by using a system that is very much linked with the volcanic nature of the possible cradle of... or the possible volcanic nature of the cradle of life. They had developed a hot/cold reactor which is water that is heated to a high temperature – 100 degrees or 110 degrees under pressure – and then very quickly it's cooled, and they find that at high temperature a number of compounds are made and if you immediately cool very quickly, they are stabilised and they are not destroyed. And they make peptides that way. They've even made nucleotides that way. So it seems to me that if peptides arise, or did arise in those days, they could possibly have catalysed in a very crude fashion some of the reactions that are catalysed today by enzymes, protein enzymes. After all, protein enzymes are peptides and they almost certainly, for reasons that I don't want to discuss... they almost certainly arose from... the proteins of today arose from small peptides, maybe not more than... maybe ten... twenty amino acids long. So those peptides, at short, could have catalytic activities, and peptides are the most likely to reproduce some of the three dimensional configurations that are involved in enzyme catalysis... in protein enzyme catalysis. So for all those reasons, I think maybe early life was... the early reactions that led to life may have been catalysed by... by... partly by peptide catalysts together with minerals, metals, and so on. And, well, my friends tell me, 'Well, that cannot be the case because how are you going to reproduce those peptides? You can't reproduce unless you have replication, and replication came with RNA' – we were talking about before RNA. Well, I'm saying, well, that's a problem for anything that happened before RNA, the reproduction. If RNA was the first molecule to be replicated, by definition what preceded RNA must have been non-replicable. But in chemistry you have a law that, if the conditions are the same, the results will be the same. So all you need is an environment that was conducive to making the peptides and... and allowing the peptides to act. And second condition: this environment must have been stable enough for the process to proceed. And it's very easily conceived that if you're dealing with strictly chemical reactions, that would lead, let us say, from a mixture of bases and riboles and phosphates to the first nuclear... say, triphosphate molecules and from those molecules to RNA. It's easy to conceive that this must have been fast, because we're dealing with chemistry and if... therefore we are dealing with chemical kinetics, and you can't imagine a process with a number of steps in which these steps would be very slow. It would take millennia to... to reach a reasonable concentration, or millions of lives, as has sometimes been claimed. The intermediary would never reach a high enough concentration to participate in the next reaction, because they would go into all side... side directions. And so it must have been fast; and that is essentially the view, of course, expressed very simply that I have tried to advocate for the origin of life, and a view that would have inspired experimental work that I would have done if I were thirty years younger.

Belgian biochemist Christian de Duve (1917-2013) was best known for his work on understanding and categorising subcellular organelles. He won the Nobel Prize in Physiology or Medicine in 1974 for his joint discovery of lysosomes, the subcellular organelles that digest macromolecules and deal with ingested bacteria.

Listeners: Peter Newmark

Peter Newmark has recently retired as Editorial Director of BioMed Central Ltd, the Open Access journal publisher. He obtained a D. Phil. from Oxford University and was originally a research biochemist at St Bartholomew's Hospital Medical School in London, but left research to become Biology Editor and then Deputy Editor of the journal Nature. He then became Managing Director of Current Biology Ltd, where he started a series of Current Opinion journals, and was founding Editor of the journal Current Biology. Subsequently he was Editorial Director for Elsevier Science London, before joining BioMed Central Ltd.

Tags: peptides, amino acids, enzymes, origin of life, RNA, replication

Duration: 5 minutes, 44 seconds

Date story recorded: September 2005

Date story went live: 24 January 2008