Abstract

In our screening to search inhibitors of phosphoinositide(PI)-specific phospholipase C (PI-PLC), two inhibitors, MT965-A and-B were isolated from a culture broth of an actinomycetes. MT965-A and-B were identified as fatty acid deribatives, 14-methylpentadecanoic acid and 16-methyllinoleic acid methyl ester, respectively, based on the spectral data including NMR and MS. Both inhibitors directly inhibited not only in vitro PLCγ1 activity but also the platelet-derived growth factor(PDGF)-induced inositol phosphates(IPt) formation in NIH 3T3γ1 cells ocerexpressing PLCγ1. However, the inhibitors enhanced in vitro protein kinase C (PKC) activity. On examination of the effects of various fatty acids(FAs) on activities of PLC, PKC, and PDGF-induced IPt formation, the unsaturated FAs(UFAs) showed the same activities like the inhibitors, but the saturated FAs(SFAs) did not show similar activities. It was inferred that the chain length, degree of unsaturation, methyl esterification, branching with a methyl group, and cis-configuration were important for their activity.

• Keywords: Phospholipase C; actinomycetes; fatty acids; inositol phosphatesm protein kinase C