From food to fuel

"The end result of metabolising a bowl of breakfast cereal and lighting it on fire are effectively the same, but our bodies choose the former", explains Professor Lancaster. "The organisms we study – and the proteins they use to catalyse their metabolic reactions – have had to evolve chemical strategies for controlled energy release."

The team have studied an enzyme called cytochrome P460, which enables organisms that use nitrogen as fuel (rather than sugar) to release energy from hydroxylamine. Hydroxylamine is potentially explosive, so it’s important that the energy is released in a controlled manner.

"We show that the presence of a single amino acid in the enzyme cytochrome P460 is vital for enabling this controlled release of energy," says Professor Lancaster.

The team made this discovery when they noticed that one variant of P460 was unable to react with hydroxylamine, despite being almost identical to the active variants. Enzymes are large and sprawling molecules with a complex structure, but it turns out that one small fragment in the outer sphere of the structure makes the difference between an active enzyme and an inactive protein.

In the inactive variant of P460, this fragment – a glutamate residue – was absent. Everything else about the two variants studied was identical, leading the researchers to conclude that this glutamate residue was the key to the enzyme’s activity

This discovery has potential long-term implications, since it advances our understanding of how controlled energy release from chemical fuels actually works. As well as helping us understand how energy release works in living organisms, it could also help us design alternative energy sources in the future.

This article is free to read in our open access, flagship journal Chemical Science: Kyle M. Lancaster et al., Chem. Sci., 2019, Advance Article. DOI: 10.1039/C9SC00195F. You can access our 2019 ChemSci Picks in this article collection.