A new enzyme function may have implications for HIV inhibitor discovery, suggests a study online this week in Nature Chemical Biology.

RK-682 is a potent inhibitor of HIV-1 proteinase, one of the enzymes necessary for HIV infectivity. This natural product found in some bacteria also contains an unusual 'tetronate' ring which is shared by several other compounds, but the pathway to make this structure is not known.

Peter Leadlay, Yuhui Sun and colleagues identify a single enzyme, RkD, as being responsible for stitching up two molecules at two sites to create a single compound containing the tetronate ring. Although it remains to be seen whether related enzymes will have exactly the same function, this work should provide new inspiration for the creation of potential HIV drugs.