 Boronic acids are known to bind to active site serines and are part of inhibitors for porcine pancreatic lipase, subtilisin and the protease Kex2.Furthermore, boronic acid derivatives constitute a class of inhibitors for human acyl-protein thioesterase 1 and 2, which are cancer drug targets within the Ras cycle.The boronic acid functional group is reputed to have low inherent toxicity.