CYSTEINE PROTEASE INHIBITORS PRODUCED BY THE INDUSTRIAL KOJI MOLD, ASPERGILLUS-ORYZAE O-1018

Aspergillus oryzae O-1018 (FERM P-15834) separated from industrial koj i for brewing sake was found to produce five papain-inhibitory compoun ds in the culture supernatant. The five isolated inhibitors were named CPI-1 to CPI-5, and their structures were elucidated by spectroscopic analyses and chemical degradation. We determined the structures of CP I-2, CPI-3 and CPI-4 as 4-amino-1-[[N-[(2S, arboxyoxiran-2-carbonyl]-L -isoleucyl]amino]butane, 5-amino-1-[[N-[(2S, arboxyoxiran-2-carbonyl]- L-isoleucyl]amino]pentane and N8-[N-[(2S, -carboxyoxiran-2-carbonyl]-L -isoleucyl]spermidine, respectively. We also confirmed by a degradatio n experiment that CPI-1 consisted of L-trans-epoxysuccinic acid, L-tyr osine and spermidine, and that CPI-5 was composed of L-trans-epoxysucc inic acid, L-phenylalanine and spermidine. Although CPI-4 was identifi ed as kojistatin A(1)), the other CPIs seemed to be novel compounds. A ll CPIs were cysteine protease-specific inhibitors with appreciable se lectivity toward cathepsin B and L. The inhibition potency of CPIs aga inst cysteine proteases was as high as or higher than that of E-64. In particular, CPI-2, -3 and -4 were ten times more effective than E-64 toward cathepsin B and L, and CPI-1 and -5 were about 100 times more i nhibitory than E-64 toward cathepsin L.