Metabolic networks provide clues about the earliest stages of enzyme evolution

The enzymes found in modern organisms are complex proteins, often with multiple folded substructures and specialized catalytic sites. Proteins are encoded by genes. Tracing the history of enzymes across all living organisms through gene comparisons leads to the last universal common ancestor (LUCA), a hypothetical organism that existed around 4 billion years ago and is believed to be the ancestor of life forms on Earth.

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