Tyropeptins A and B, new proteasome inhibitors, were isolated from the culture broth of Kitasatospora sp. MK993-dF2. They were purified using ethyl acetate extraction, silica gel column chromatography, Sephadex LH-20 column chromatography and HPLC. Tyropeptin A inhibited the chymotrypsin-like (ChT-L) and trypsin-like (T-L) activities of 20S proteasome with IC₅₀ values of 0.1μg/ml and 1.5μg/ml respectively, but did not inhibit the peptidylglutamyl-peptide hydrolyzing (PGPH) activity of 20S proteasome at a concentration of 100μg/ml. The inhibitory activities of tyropeptin A were about two times as strong as that of tyropeptin B. Taxonomy of the producing strain is also described.

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The structures of tyropeptins A and B, new proteasome inhibitors produced by Kitasatospora sp. MK993-dF2, were determined by analysis of various NMR experiments. The ¹H and ¹³C NMR of tyropeptins were complicated due to the presence of an aldehyde group. Therefore, tyropeptins were converted to their alcohols by sodium borohydride. These alcohol derivatives gave assignable NMR spectra. The stereochemistry of tyropeptins were determined by analysis of acid hydrolysis products from tyropeptins, and further confirmed by the total synthesis. The structures of tyropeptins A and B were found to be isovaleryl-L-tyrosyl-L-valyl-DL-tyrosinal and n-butyryl-L-tyrosyl-L-leucyl-DL-tyrosinal, respectively.

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Glutamate, an excitatory amino acid, is known to induce neurotoxicity in central nervous system under abnormal conditions such as ischemia, hypoglycemia, epilepsy, Huntington's chorea, Parkinson's disease and Alzheimer's disease. In our search for neuroprotective agents of microbial origin against excitatory neurotoxins, we have isolated two new bicyclohexapeptides, neuroprotectins A and B, together with a known compound complestatin, from the fermentation broth of Streptomyces sp. Q27107. Neuroprotectins protected primary cultured chick telencephalic neurons from glutamate- and kainate-induced excitotoxicities in a dose-dependant fashion.

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In the course of our search for neuroprotective agents of microbial origin against kainateinduced neurotoxicity, we have succeeded in the isolation of two new bicyclohexapeptides, neuroprotectins A and B, together with a known compound, complestatin, from the fermentation broth of Streptomyces sp. Q27107. They are closely related in structure to complestatin and possess an oxindolylalanine moiety in place of the tryptophan residue present in complestatin.

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Two new squalene synthase (SSase) inhibitors, CJ-13, 981 (I) and CJ-13, 982 (II), were isolated from the fermentation broth of an unidentified fungus CL15036. They inhibited human liver microsomal SSase with IC₅₀s of 2.8 and 1.1 μM, respectively, but showed no inhibitory activity against human brain protein farnesyltransferase (PFTase) at 100 μM. Based on FAB-MS and NMR analyses, the structures of I and II were determined to be 3-hydroxy-3, 4-dicarboxy15-hexadecenoic acid and 3-hydroxy-3, 4-dicarboxyhexadecanoic acid, respectively.

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A new antifimgal agent, CJ-19, 784 (I), was isolated from the fermentation broth of a fungus, Acanthostigmella sp. CL12082. Based on spectroscopic analyses, structure of I was determined to be 3'-bromo-2', 5-dihydroxy-3, 7, 8-trimethoxy-flavone. Compound I inhibits the growth of pathogenic fungi, Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus with IC₅₀ values of 0.11, 20 and 0.54 μg/ml, respectively.

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Streptomycetes, which belong to the Gram-positive bacteria, produce secondary metabolites and sporulate. The timing of starting the secondary metabolite production and the sporulation depends on environmental conditions such as nitrogen and carbon sources. In order to obtain a tool for understanding the regulation mechanism, we carried out screening for chemical substances that induce secondary metabolism and sporulation in Streptomycetes and found an active substance from the culture broth of Streptomyces sp. TP-A0584. This substance designated goadsporin promoted the formation of red pigment and sporulation at a concentration of 1 μM in Streptomyces lividans TK23 which does not produce the pigment under normal growth conditions. Goadsporin is an oligopeptide consisting of 19 amino acids with the molecular formula C₇₂H₉₇N₁₉O₂₀S₂. Sporulation and/or secondary metabolite production was induced in 36 Streptomycetes strains among 42 strains tested. These results suggest that goadsporin acts on a common regulation pathway for sporulation and secondary metabolism in Streptomycetes and can be a powerful tool to analyze the regulation mechanism.

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The structure of goadsporin was determined by using spectroscopic techniques. NMR analysis revealed that goadsporin consists of 19 amino acids, two of which are dehydroalanines (Deala), and six of which are cyclized to oxazoles (Oxz) and thiazoles (Thz) by dehydrative cyclization and dehydrogenation from serine, threonine and cysteine. NMR analysis established seven partial structures, and their sequence was determined by CID-MS/MS'. Negative mode FAB-MS/MS gave product ions arising from charge-remote fragmentation that allowed determination of the sequence of the amino acid components as AcNH-Ala-MeOxz-Val-Deala-MeOxz-Ile-Leu-Thz-Ser-Gly-Gly-MeOxz-Leu-Deala-Oxz-Ala-Gly-Thz-Val-OH. The chiral amino acids were determined by the advanced Marfey's method to have L-configurations.

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Peptide antibiotics tripropeptins A, B, C, D and Z were isolated from cultured cells and broth of Lysobacter sp. The differences among these components are in the lengths of the alkyl side chain. Tripropeptins are active against Gram-positive bacteria including MRSA in vitro. Bactericidal activity of tripropeptin C disappeared in the simultaneous presence of chloramphenicol, a bacteriostatic agent.

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A novel antibiotic, CJ-15, 801 (I), was isolated from the fermentation broth of a fungus, Seimatosporium sp. CL28611. The structure was determined to be a pantothenic acid analog having an α, β-unsaturated carboxylic acid moiety by spectroscopic analyses. The compound inhibits the growth of multi-drug resistant (MDR) Staphylococcus aureus strains with MIC ranging from 6.25 to 50μml

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The biosynthesis of the antibiotic GE2270 in the producing microorganism Planobispora rosea was investigated by adding labelled amino acid precursors. Efficient incorporation of glycine and serine was observed, leading to specific enrichments of selected positions of the thiazole, oxazoline and pyridine rings. Furthermore, efficient enrichment of the C-, N- and O-methyl groups was detected. These results indicate that GE2270 is made through a biosynthetic route similar to that determined for other thiazolylpeptides. At the same time, the result point to an efficient route for the conversion of glycine into serine and methyl equivalents in Planobispora rosea.

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Biological and biochemical activities of resormycin were studied using unicellular green algae, Selenastrum capricornutum (abbreviated as Selena.), as a test organism. Resormycin inhibited the growth in vitro of Selena, more strongly in the dark than in the light. A weaker but more photo-stable derivative, (±)-2, 3-dihydro-resormycin, showed more long-lasting activity against Selena, in the light. Resormycin started killing Selena, only after exposure for 2 days and longer, even at high concentrations. Resormycin at concentrations near IC₅₀ rapidly inhibited incorporation of ³H-leu, but not ³H-UR or ³H-TdR, into the TCA insoluble fraction of Selena. Herbicidal activity of resormycin was confirmed using some crops and weeds.

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Novel 1β-methyl carbapenems with a cycloalkylamine moiety as a side chain were synthesized and their structure-activity relationships were studied. These carbapenems showed potent antibacterial activities against a wide range of Gram-positive and Gram-negative bacteria, and moderate urinary recovery when administered intraperitoneally in mice.

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