Structure-activity Relationship of Pamamycins: Effect of Side Chain Length on Aerial Mycelium-inducing Activity

Abstract

Two pamamycin homologues with different side chain lengths were isolated from Streptomyces sp. HKI-0118. Aerial mycelium-inducing activity decreased by ca. 1/10 per methylene unit in the side chain.Keywords pamamycin, structure-activity relationship, aerial mycelium, differentiation, polyketide Pamamycins are unique polyketides containing a nitrogen atom [1,2]. Pamamycins were discovered as aerial mycelium-inducing substances of Streptomyces alboniger by McCann and Pogell [3], and their isolation and structural elucidation were accomplished by our group [4ϳ6]. Pamamycin-607 (3), a major active component with MW 607, induces or stimulates aerial mycelium formation and regulates secondary metabolite production in many Streptomyces spp. in addition to the species in which it is produced [7].We have examined the structure-activity relationship of pamamycins by isolating homologues [8,9] and de-Nmethyl derivatives from cultured material of S. alboniger [10,11] and by preparing derivatives [12]. We have determined that the nitrogenous group is indispensable to aerial mycelium-inducing activity, that de-N-methylation increases this activity 1.5 times, and that substitution of the methyl group at R 3 or R 4 with an ethyl group markedly lowers activity.To refine our understanding of the structure-activity relationship around the nitrogenous group, we planed to isolate homologues with different side chain lengths and to examine their aerial mycelium-inducing activity. There are two reports on such homologues: MS-282a and MS-282b were isolated from S. tauricus ATCC 27470 as inhibitors of calmodulin-activated myosin light chain kinase [13]. Härtl et al. reported the production of various lengths of the nitrogen-containing side chain of pamamycin (nϭ2ϳ4 in Fig. 1) by Streptomyces sp. HKI-0118 and S. aurantiacus IMET 43917 [14], but they were unsuccessful in isolating these components.We report the isolation of two pamamycin homologues, 1 and 2, with different side chain lengths from Streptomyces sp. HKI-0118 ( Fig. 1) and describe their aerial myceliuminducing activity.Streptomyces sp. HKI-0118 was cultured in 2.0-liter Erlenmeyer flasks containing 1.0 liter of glucose -oat meal -yeast extract medium [14] at 28°C for 7 days on a rotary shaker (150 rpm). The fermentation broth (26 liters) was separated into filtrate and mycelia, then the filtrate was treated with EtOAc at pH 8 and the mycelia were macerated in Me 2 CO. The Me 2 CO extract of mycelia was

Microparticles globally reprogram Streptomyces albus toward accelerated morphogenesis, streamlined carbon core metabolism, and enhanced production of the antituberculosis polyketide pamamycin

“…It would be interesting to further explore this link in other natural producers, which obviously differ in the spectrum of pamamycin homologues (Natsume, Yasui, Kondo, & Marumo, 1991;Natsume et al, 1995;Kozone, Chikamoto, Abe, & Natsume, 1999). Metabolic engineering of CoA-ester supply appears promising to streamline pamamycin production towards selective derivatives (Lu, Zhang, Jiang, & Bai, 2016).…”

Discovery and overproduction of novel highly bioactive pamamycins through transcriptional engineering of the biosynthetic gene cluster

“…In fact, homopamycin 677A could be seen as an outcome of such starter unit selection: in the case of hydroxy acid small instead of usual propionate the butyrate is used. This compound is the first reported pamamycin with the extension of hydroxy acid small, since all other derivatives with the other than propionate starter had longer hydroxy acid large (homopamamycin 621A and bishomopamamycin 635A) [23].…”

“…). Since all known pamamycins 635, 635A, 635F [33,37] and bis-homopamamycin-635A [24] bear at least two doublet methyls, pamamycin 635G must be a new pamamycin. 2D NMR 5A).…”

“…At the same time, to date, only two Fig. 1 Chemical structures of pamamycin derivatives with side chain substitution patterns pamamycins are known in which the hydroxy acid L (18C) is extended by one or two additional methylene groups: homopamamycin 621A (hydroxy acid L-19C) and bishomopamamycin 635 (hydroxy acid L-20C) [23]. "Light" pamamycins (such as pam-607, pam-621A, etc.)…”

New Insights into the Synthesis and Biological Activity of the Pamamycin Macrodiolides

“…The structure-activity relationship of pamamycins has mainly been studied by Natsume et al In a recent report, [29] they determined the effect of side chain length on aerial mycelium-inducing activity by isolating two pamamycin side chain homologues from Streptomyces sp HKI-0118: homopamamycin-621A (R 1 -R 5 identical to 1b, n = 3, Fig. 2) and bishomopamamycin-635A (R 1 -R 5 identical to 1b, n = 4, Fig.…”