Propioxatins A and B, new enkephalinase B inhibitors. I. Taxonomy, fermentation, isolation and biological properties.

A soil isolate of actinomycete, strain SANK 60684, was found to produce new enkephalinase B inhibitors, propioxatins A and B. The presence of both LL- and meso-2,6-diaminopimelic acid, glycine and galactose in the cell wall assigned this strain to genus Kitasatosporia. From the morphological, cultural and physiological characteristics, this strain was determined to be Kitasatosporia setae. The Ki values of propioxatins A and B were 1.3 X 10(-8)M and 1.1 X 10(-7)M, respectively, for enkephalinase B. All other proteases examined except aminopeptidases, which were slightly inhibited, were not inhibited by these two compounds.