Surprising enzymes found in giant ocean viruses

A new study by researchers at the Woods Hole Oceanographic Institution (WHO) and Swansea University Medical School deepens our understanding of viruses – at sea and on land – and their potential to cause life-threatening diseases. Their discoveries, which focus on newly identified genes carried by mysterious "giant" viruses, could represent potential new targets for drugs against giant viruses linked to human diseases. The work published this week in Proceedings of the National Academy of Sciences.

An international team of researchers has examined more than 8,000 virus genomes and discovered that many recently discovered giant viruses contain several genes for one type of enzyme called cytochrome P450. P450 enzymes are common in animals, plants and bacteria, but their discovery in new viruses is unexpected. Before giant viruses, it was never thought that viruses would have these genes.

"This is an extremely interesting discovery," says biologist John Stegeman, lead author of the journal and director of the Woods Hole Center for Oceans and Human Health at WHOI. "In animals, P450 enzymes metabolize drugs, make steroid hormones, and defend themselves against pollutants, and we have not yet discovered what they do with these viruses, but it is certain that they are safe." they are unique, unlike the P450s of any other organism. "

P450 enzymes, which are one of the largest known super-families of enzymes, can also have major implications for understanding the effects of chemicals at sea and in human disease processes.

"We know that some giant viruses can be linked to some forms of pneumonia, so understanding them better will help us develop ways to fight these viruses," said David Lamb, principal author of Swansea University Medical School. in Wales. working on research at OMSI on a Fulbright Scholarship.

"The P450 could represent therapeutic targets for giant viruses that would contribute to some pneumonia," said Stegeman.

The discovery of P450 genes and enzymes in various viruses opens a new window on the evolution of these important enzymes, which can help to understand the biology and origin of the giant viruses themselves, which is currently unknown and is hotly debated, says Stegeman.

Viruses are the most numerous biological "entities" on Earth, although giant viruses have only been known in 2003, when a virus powerful enough to be observed under an optical microscope was discovered. More than 1,000 genes have been identified in this first giant virus; in comparison, the influenza virus contains 14 genes. Since then, other giant viruses containing many more genes and more P450 have been discovered around the world, some with nearly 3,000 genes. More and more giant viruses are being discovered in the oceans, including in the deep sea.