HIV-1 protease inhibitors: Ketomethylene isosteres with unusually high affinity compared with hydroxyethylene isostere analogs

HIV protease is a member of the aspartic proteinase family of proteolytic enzymes which include pepsin and renin. In contrast to the enhanced affinity seen with renin and pepsin upon conversion of the transition-state isostere, ketomethylene, to the hydroxyethylene, a set of HIV protease inhibitors showed a reduction in affinity. This implies that interactions with the active site of other segments of the inhibitor than those of the transition-state analog must predominate in the case of HIV protease, and that observations made on mammalian aspartic proteinases do not necessarily apply to viral aspartic proteinases.