ABSTRACT
Fatty-acid biosynthesis by a branched-chain alpha-keto acid dehydrogenase (bkd) mutant of Streptomyces avermitilis was analyzed. This mutant is unable to produce the appropriate precursors of branched-chain fatty acid (BCFA) biosynthesis, but unlike the comparable Bacillus subtilis mutant, was shown not to have an obligate growth requirement for these precursors. The bkd mutant produced only straight-chain fatty acids (SCFAs) with membrane fluidity provided entirely by unsaturated fatty acids (UFAs), the levels of which increased dramatically compared to the wild-type strain. The levels of UFAs increased in both the wild-type and bkd mutant strains as the growth temperature was lowered from 37 degrees C to 24 degrees C, suggesting that a regulatory mechanism exists to alter the proportion of UFAs in response either to a loss of BCFA biosynthesis, or a decreased growth temperature. No evidence of a regulatory mechanism for BCFAs was observed, as the types of these fatty acids, which contribute significantly to membrane fluidity, did not alter when the wild-type S. avermitilis was grown at different temperatures. The principal UFA produced by S. avermitilis was shown to be delta 9-hexadecenoate, the same fatty acid produced by Escherichia coli. This observation, and the inability of S. avermitilis to convert exogenous labeled palmitate to the corresponding UFA, was shown to be consistent with an anaerobic pathway for UFA biosynthesis. Incorporation studies with the S. avermitilis bkd mutant demonstrated that the fatty acid synthase has a remarkably broad substrate specificity and is able to process a wide range of exogenous branched chain carboxylic acids into unusual BCFAs.
Subject(s)
Fatty Acids/biosynthesis , Ketone Oxidoreductases/metabolism , Multienzyme Complexes/metabolism , Streptomyces/metabolism , 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide) , Anaerobiosis , Bacillus subtilis/metabolism , Fatty Acids/metabolism , Ivermectin/analogs & derivatives , Ivermectin/metabolism , Ketone Oxidoreductases/genetics , Multienzyme Complexes/genetics , Mutation , Streptomyces/genetics , TemperatureABSTRACT
A kappa opioid receptor binding inhibitor was isolated from the fermentation broth of a basidiomycete, Hericium ramosum CL24240 and identified as erinacine E (1). Three analogs of 1 were produced by fermentation in other media and by microbial biotransformation. Of these compounds, 1 was shown to be the most potent binding inhibitor. Preliminary SAR studies of these compounds indicated that all functional groups and side chains were required for the activity. Compound 1 was a highly-selective binding inhibitor for the kappa opioid receptor: 0.8 microM (IC50) for kappa, >200 microM for mu, and >200 microM for delta opioid receptor. Compound 1 suppressed electrically-stimulated twitch responses of rabbit vas deferens with an ED50 of 14 microM. The suppression was recovered by adding a selective kappa opioid receptor antagonist nor-binaltorphimine, indicating that 1 is a kappa opioid receptor agonist.
Subject(s)
Benzofurans/pharmacology , Receptors, Opioid, kappa/agonists , Spiro Compounds/pharmacology , Animals , Basidiomycota , Benzofurans/chemistry , Benzofurans/isolation & purification , Chromatography, High Pressure Liquid , Electric Stimulation , Fermentation , Guinea Pigs , Male , Rabbits , Receptors, Opioid, kappa/metabolism , Spiro Compounds/chemistry , Spiro Compounds/isolation & purification , Structure-Activity Relationship , Vas Deferens/drug effects , Vas Deferens/metabolismABSTRACT
A soil isolate produced a novel extracellular polysaccharide (EPS) with unusually potent thickening powers. The EPS contained d-mannose, d-glucose, d-galactose, and d-glucuronic acid in the unique molar ratio 1:4:1:2 and 10 to 15% acetate. Viscosities of a 1-g/liter aqueous solution were 1 x 10 and 14 x 10 cP at shear rates of 0.01 and 0.1 s, respectively. The EPS was insensitive to high concentrations of NaCl and CaCl(2).
