Cycloheximide is a highly effective antibiotic with activity against mold, yeast, and phytopathogenic fungi, with lower activity against bacteria. It has been reported to inhibit the synthesis of both proteins and macromolecules, as well as affect apoptosis in eukaryotes. Inhibition of protein synthesis is believed to be mediated through DNA translation arrest, as demonstrated in rat thymocytes. Although cycloheximide has been reported to induce apoptosis in various cells, it has also been shown to inhibit or delay induced apoptosis. These observations suggest that cycloheximide's effect on apoptosis may not be solely through protein translation arrest and that other mechanisms may be involved. Cycloheximide has also been reported to inhibit FKBP12 (peptidylprolylisomerase hFKBP12, PPIase hFKBP12) via competitive inhibition.
