K-252a, a metabolite isolated from the culture broth of Nocardiopsis sp. K-252a, was found to exhibit an extremely potent inhibitory activity on protein kinase C. The IC50 value was 32.9 nM.
Nocardiopsis sp. K-290 was found to produce novel metabolites, designated K-252b, c and d, which were structurally related to K-252a. These compounds were isolated from the culture broth and the physico-chemical and biochemical properties were examined. The compounds strongly inhibited protein kinase C. IC50 values (the concentrations causing 50 inhibition) for the effects of K-252b, c and d on the rat brain enzyme were 38.3, 214, and 337 nM, respectively. In a previous paper1), we reported that Nocardiopsis sp. K-252 produced a potent and new protein kinase C inhibitor, K-252a (1). In the present investigation, we have isolated three compounds, designated K-252b (2), c (3) and d (4), which are structurally related to K-252a, from the culture broth of Nocardiopsis sp. K-290. Similar to K-252a, these compounds strongly inhibited protein kinase C. This paper deals with fermentation, isolation and purification, and some biochemical properties of K-252b, c and d. Structural elucidation studies will be described in a succeeding paper2). Materials and Methods Microorganisms Nocardiopsis sp. K-290, isolated from a soil of Tama-shi, Tokyo, Japan, was employed in the present studies. Taxonomy of the strain will be described in a separate paper.
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