Metals could have catalyzed amino acid synthesis on early Earth

Amino acids are molecules fundamental to living organisms because they combine to build proteins, the workhorses of the cell. One metabolic pathway that produces amino acids involves transamination, a reaction in which an amino group is transferred to a keto acid. Normally, an enzyme or a cofactor catalyzes transamination. But Joseph Moran, a chemist at the University of Strasbourg, wondered whether this process happened without enzymes in the earliest days of life on Earth.

At high temperatures, metal ions can catalyze transamination. A new study shows that several metals likely abundant on early Earth can do the catalysis under biological conditions, at room temperature (J. Am. Chem. Soc. 2021, DOI: 10.1021/jacs.1c08535). The study’s top performers, which produced the highest yield of amino acids, were copper, cobalt, vanadium, and nickel.

Moran and his team conducted multiple analyses to determine how these metals catalyze the amino group transfer. “The metals essentially work in two different ways,” Moran says. Copper and cobalt stabilize an intermediate imine, and vanadium accelerates the reaction by increasing the acidity of a key C–H bond. Nickel does a bit of both.

Moran says the results support the idea that the chemical framework for metabolism could have been present from the start, before complex proteins and genetic molecules like RNA evolved on Earth.