Suicide of a protein

摘要

Thiamine is an essential cofactor that allows important enzymes to catalyse metabolic reactions. Humans depend on their diet to supply it as vitamin B_p but bacteria, plants and yeast can make their own. They do this by bringing together two precursor molecules: a sulphur-containing ring structure known as a thiazole and a nitrogenous pyrimidine. But the biochemical origin of the thiazole component of thiamine in plants and fungi has been mysterious - until now. On page 542 of this issue, Chatterjee and co-workers1 describe a highly unusual reaction step in which a sulphur atom is transferred from a protein's amino-acid residue, to become part of the thiazole precursor. The donor protein is therefore functioning as a reagent, or 'suicide enzyme', rather than as a conventional catalytic enzyme.