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Biomedical subjects

Yasuhiro Igarashi

Publications and source records attributed to Yasuhiro Igarashi.

41 records · Page 3Linked to original sources
PubMed2002

Biosynthesis of hibarimicins. I. 13C-labeling experiments.

Biosynthesis of hibarimicin was studied based on the feeding experiments with 13C labeled acetates. All carbons in the aglycon, except for the methoxy carbons, were derived from acetate. The carbon framework of the aglycon was proved to be constructed by dimerization of an intermediate which was biosynthesized via the decarboxylation and skeltal rearrangement starting from an undecaketide. The rearrangement was confirmed by detecting the long range (three-bond) coupling between two carbons in the difference spectra of selective 13C decoupled INADEQUATE of hibarimicin B labeled with sodium [1,2-13C2] acetate.

Anti-Bacterial Agents↗
PubMed2002

Biosynthesis of hibarimicins. II. Elucidation of biosynthetic pathway by cosynthesis using blocked mutants.

The biosynthetic pathway of hibarimicin (HBM) was proposed on the basis of the experimental results obtained by using blocked mutants of Microbispora rosea subsp. hibaria TP-A0121, the HBM producer. In its biosynthesis, the oxidative coupling of the aromatic undecaketide unit generates a symmetrical aglycon HMP-Y1 (hibarimicin-mutant product Y1), which is oxidatively modified to hibarimicinone, the HBM aglycon. The following glycosylation of hibarimicinone gives rise to the HBM complex. We identified that HMP-Y1 prepared by methanolysis of HMP-Y6, a glycosylated metabolite from a blocked mutant, was the key intermediate: transformation of 13C-labeled HMP-Y1 to HBM B was confirmed by NMR measurements. Mutant strain produced another type of aglycon HMP-P1 in which the coupled polyketide units were intramolecularly bridged by the ether bond. This metabolite also arose by the spontaneous elimination of methanol molecule from hibarimicinone.

Anti-Bacterial Agents↗
PubMed2002

Biosynthesis of hibarimicins. III. Structures of new hibarimicin-related metabolites produced by blocked mutants.

Structures of metabolites produced by blocked mutants of Microbispora rosea subsp. hibaria TP-A0121, hibarimicin-producer, were determined by spectroscopic analysis. HMP-Y6 is the dimer of the west half of hibarimicin B, the aglycon of which is the genuine biosynthetic intermediate. HMP-P1 is the shunt product arising from the release of a methanol molecule from hibarimicinone. HMP-P4, the glycoside of HMP-P1, is glycosylated with two amicetoses and two digitoxoses same as hibarimicin B. HMP-M1, M2, M3 and M4 are shunt products derived from the monomeric undecaketide intermediates.

Anti-Bacterial Agents↗
PubMed2002

TPU-0037-A, B, C and D, novel lydicamycin congeners with anti-MRSA activity from Streptomyces platensis TP-A0598.

In screening for anti-MRSA antibiotics, novel lydicamycin congeners, TPU-0037-A, B, C and D, were isolated from a culture broth of an actinomycete strain. The producing strain, TP-A0598, was isolated from a seawater sample collected in Toyama Bay, Japan, and identified as Streptomyces platensis based on taxonomic characteristics. TPU-0037-A, B, C and D were purified by HP-20 resin, ODS column chromatographies and preparative HPLC, consecutively, and their structures were determined to be 30-demethyllydicamycin, 14,15-dehydro-8-deoxylydicamycin, 30-demethyl-8-deoxylydicamycin and 8-deoxylydicamycin, respectively, by NMR and MS analyses. The new congeners showed antibiotic activity against gram-positive bacteria including MRSA with the MIC of 1.56 to approximately 12.5 microg/ml.

Anti-Bacterial Agents↗