Tony McDonagh is in the Division of Gastroenterology, University of California San Francisco, San Francisco, California 94143-0538, USA. email: tonymcd@itsa.ucsf.edu
Biliverdin is reduced to the potent antioxidant bilirubin in mammals and other vertebrates. The X-ray crystal structures of two biliverdin reductases, with different isomer specificities, show how substrate and cofactor bind to the enzymes and provide new insights into the mechanism of the reduction.
