Actinonin is a naturally occurring antibacterial agent isolated from Actinomyces with antibiotic and anti-tumor activity. Actinonin inhibits aminopeptidase M, aminopeptidase N and leucine aminopeptidase. Actinonin is a potent reversible peptide deformylase (PDF) inhibitor with a Ki of 0.28 nM. Actinonin also inhibits MMP-1, MMP-3, MMP-8, MMP-9, and hmeprin α with Ki values of 300 nM, 1,700 nM, 190 nM, 330 nM, and 20 nM, respectively. Actinonin is an apoptosis inducer. Actinonin has antiproliferative and antitumor activities.