Lymphostin (LK6-A), a Novel Immunosuppressant from Streptomyces sp. KYI 1783: Taxonomy of the Producing Organism, Fermentation, Isolation and Biological Activities

Abstract

In the course of screening for inhibitors of the lymphocyte kinase, Lck (p56^lck), aiming at novel immunosuppressants, we isolated a novel alkaloid, lymphostin (LK6-A), from the culture broth of Streptomyces sp. KYI 1783. Lymphostin was produced in a fermentation medium supplemented with a highly porous polymer resin, which prevented the degradation of this compound in the culture broth. Lymphostin inhibited the kinase activity of Lck with an IC₅₀ value of 0.05μM, and exhibited potent inhibitory activity against the mixed lymphocyte reaction (MLR) with an IC₅₀ value of 0.009μM.