New research at Lawrence Livermore National Laboratory (LLNL) and Boston University shows that many of the complex biochemical networks that humans and other advanced organisms depend on for their existence could not have evolved without oxygen.

"You could call it the 'oxygen imperative,' " said LLNL postdoctoral researcher Jason Raymond. "It's clear that you need molecular oxygen to evolve complex life as we know it."

"Researchers have spent decades putting together maps of how the building blocks of life connect to each other," added Daniel Segr of Boston University, who holds a joint appointment in LLNL's Biosciences Directorate. "It turns out that whole regions in this map may not have existed without oxygen."

Raymond and Segr used computer simulations to study the effect of oxygen on metabolic networks the biochemical systems that enable organisms to convert food and nutrients into life-sustaining energy. Their analysis shows that the largest and most complex networks those found in humans and other advanced organisms require the presence of molecular oxygen. The research is reported in the March 24 issue of the journal Science.

"We wanted to look at how the availability of oxygen changed the types of chemical reactions," Raymond said, "both with respect to metabolites (metabolism byproducts) and to the enzymes needed to carry out metabolism."

Raymond and Segr calculated the number of possible combinations of the thousands of enzymes and chemicals involved in all known metabolic reactions across the tree of life, and came up with a "virtually limitless" number ten to the 16,536th power. Simulating that many networks would be an impossible task even for LLNL, which houses the world's most po
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Contact: Charlie Osolin
osolin1@llnl.gov
925-422-8367
DOE/Lawrence Livermore National Laboratory
23-Mar-2006