Theoretical origin of life: possible early enzymes (Introduction)

by David Turell , Saturday, June 11, 2016, 23:20 (2869 days ago) @ David Turell

This a theoretical computer study which produced a complex enzyme from very early bacteria 3.5 billion years ago. How is such complexity developed so quickly?: - https://www.newscientist.com/article/2093257-ancient-enzyme-resurrected-from-the-ancest... - "The ancestor of all bacteria may have had sophisticated enzymes 3.4 billion years ago - just 600 million years after the origin of life on Earth. - *** - "The discovery comes as a surprise since we had assumed they didn't evolve until much later - perhaps even for another billion years. - "Modern enzymes fit the molecules they react with like a lock to a key. They normally only work for one reaction, but they perform that one job very well. 
 
"In contrast, the earliest enzymes were “sloppy”, says Michael Harms of the University of Oregon - they didn't have a lock and key relationship with their molecules. - "To find out when modern enzymes arose, Reinhard Sterner at the University of Regensburg and his colleagues reconstructed a four-part enzyme as it would have looked before modern bacteria and archaea groups split. - "Called tryptophan synthase, the enzyme aids the creation of an amino acid crucial to bacteria, archaea, plants and fungi. - "First they analysed the gene that codes for the enzyme in modern bacteria and archaea, before feeding the sequences into a computer program that searched for similarities between them. - "They then ran thousands of simulations of what the ancient DNA sequence the modern genes came from might have been. - "The program landed on a sequence that was the most probable based on how the major groups of bacteria branched off from each other. The team inserted this resurrected gene into modern E. coli cells, which churned out an enzyme that behaved much like the modern versions. - "This implies bacteria lost their sloppy proteins earlier than we expected, Harms says. A recent study, for example, claimed that simpler enzymes stuck around for another billion years or more. - “It stands counter to what a lot of people would have predicted,” says Harm. “It challenges some received wisdom in the field.” - "Since no DNA remains from billions of years ago, reconstruction experiments like this are the only way to study ancient genes. - *** - "When treated with heat, the reconstructed bacterial enzyme managed to keep its structure until about 70°C. This suggests it was probably part of a microbe that lived in scalding-hot water, Groussin says. “You can infer with strong confidence that the organism lived in a hot environment,” he says. - "This confirms other scientists' hypotheses about the first bacteria living in hot water, Groussin says. - "While the first living cells probably lived in lukewarm habitats, things changed when more complex bacteria began evolving. It's possible that asteroid bombardments caused Earth's surface to sizzle during this phase of evolution, meaning that the species that survived had heat-resistant hardware." - Comment: I still think evolution is driven, never by chance.