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.

中文翻译：

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K-252b，c和d是来自微生物的有效的蛋白激酶C抑制剂。

诺卡氏菌 发现K-290产生新的代谢产物，命名为K-252b，c和d，它们在结构上与K-252a有关。从培养液中分离这些化合物，并检查其理化和生化特性。该化合物强烈抑制蛋白激酶C。K-252b，c和d对大鼠脑酶的作用的IC50值（引起50％抑制的浓度）分别为38.3、214和337 nM。