Prolyl endopeptidase inhibitors derived from actinomycetes

Four prolyl endopeptidase inhibitors isolated from actinomycetes, named propeptin, SNA-8073-B, staurosporine, and enduracidin were classified into 3 groups on the basis of their inhibition potency against prolyl endopeptidase from a bacterium (Flavobacterium) and a mammal (human placenta). Staurosporine inhibited the enzyme from Flavobacterium more strongly than that from human placenta. Enduracidin inhibited the enzyme from human placenta more strongly than that from Flavobacterium. Propeptin and SNA-8073-B, both new compounds, inhibited the enzymes from both origins to the same extent.