Shunichi Miyakoshi

Synthesis and antimycobacterial activity of capuramycin analogues. Part 1: substitution of the azepan-2-one moiety of capuramycin

Capuramycin analogues with a variety of substituents in place of the azepan-2-one moiety were synthesized from A-500359E and were tested for their translocase I inhibitory activity and in vitro antimycobacterial activity. Phenyl-type moieties were found to be effective substituents for capuramycin analogues.

Synthesis and antimycobacterial activity of capuramycin analogues. Part 2: acylated derivatives of capuramycin-related compounds.

Acylated derivatives of capuramycin and A-500359A were synthesized and tested for antimycobacterial activity. Compound 20 having a decanoyl group showed very potent activity.

A-102395, a New Inhibitor of Bacterial Translocase I, Produced by Amycolatopsis sp. SANK 60206

Bacterial phospho-N-acetylmuramyl-pentapeptide translocase (translocase I: EC 2.7.8.13) is a key enzyme in peptidoglycan biosynthesis, and a known target of antibiotics. Here we report a new nucleoside inhibitor for translocase I, A-102395, isolated from the culture broth of the strain Amycolatopsis sp. SANK 60206. A-102395 is a new derivative of capuramycin that has the benzene with a uniquely substituted chain instead of an aminocaprolactam. A-102395 is a potent inhibitor of bacterial translocase I with IC50 value of 11 nM, but possesses no antimicrobial activity against various strains tested.

FKS1 Mutations Responsible for Selective Resistance of Saccharomyces cerevisiae to the Novel 1,3-β-Glucan Synthase Inhibitor Arborcandin C

ABSTRACT Arborcandin C is a novel antibiotic with potent antifungal activity that inhibits 1,3-β-glucan synthase in fungi. We examined spontaneous Saccharomyces cerevisiae mutants which are selectively resistant to arborcandin C and revealed that a single amino acid replacement in Fks1p of Asn470 with Lys or of Leu642 with Ser confers selective resistance on Fks1p mutants.

A-94964, a novel inhibitor of bacterial translocase I, produced by Streptomyces sp. SANK 60404. I. Taxonomy, isolation and biological activity.

Bacterial phospho-N-acetylmuramyl-pentapeptide translocase (translocase I: EC 2.7.8.13) is a key enzyme in peptidoglycan biosynthesis, and a known target of antibiotics. Here we report a novel nucleoside inhibitor against translocase I, A-94964, isolated from the culture broth of the strain Streptomyces sp. SANK 60404. A-94964 inhibited bacterial translocase I with IC50 value of 1.1 μg/ml, and showed antimicrobial activities against Staphylococcus aureus and Enterococcus faecalis with MIC of 100 and 50 μg/ml, respectively. A-94964 did not show cytotoxicity against mammalian cell lines.

Synthesis and antimicrobial activity of novel globomycin analogues.

Globomycin, a signal peptidase II inhibitor, and its derivatives show potent antibacterial activity against Gram-negative bacteria. The synthesis and antimicrobial activity of novel globomycin analogues are reported. One of the analogues showed a more potent activity against Gram-negative bacteria than globomycin and also exhibited antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA).

A-94964, Novel Inhibitor of Bacterial Translocase I, Produced by Streptomyces sp. SANK 60404 : II. Physico-chemical Properties and Structure Elucidation

In our screening for translocase I inhibitors, we found the novel nucleoside antibiotic, A-94964 in the culture broth of Streptomyces sp. SANK 60404. The structure of A-94964 was elucidated primarily by various NMR studies, including a 1H-31P HMBC experiment. A-94964 has a unique structure which possesses a nucleoside moiety and an N-acylglucosamine moiety connected via a phosphate.

Studies on novel bacterial translocase I inhibitors, A-500359s. V. Enhanced production of capuramycin and A-500359 A in Streptomyces griseus SANK 60196.

Streptomyces griseus SANK 60196 produces the novel nucleoside antibiotics A-500359 A, C, D and capuramycin. Enhanced production of capuramycin and A-500359 A was achieved through a number of medium modifications and a series of single colony isolations. The addition of maltose instead of glucose as the carbon source in a primary medium resulted in a 20-fold increase in the productivity of capuramycin. Furthermore, the addition of cobalt chloride (CoCl2) and yeast extract to the medium containing maltose drastically altered the production ratio of A-500359 A to capuramycin. Thus, the yield of A-500359 A increased up to 600 μg/ml in an optimal medium, while the yield in the primary medium was 1 μg/ml.

A novel assay of bacterial peptidoglycan synthesis for natural product screening.

Although a large number of microbial metabolites have been discovered as inhibitors of bacterial peptidoglycan biosynthesis, only a few inhibitors were reported for the pathway of UDP-MurNAc-pentapeptide formation, partly because of the lack of assays appropriate for natural product screening. Among the pathway enzymes, D-Ala racemase (Alr), D-Ala:D-Ala ligase (Ddl) and UDP-MurNAc-tripeptide:D-Ala-D-Ala transferase (MurF) are particularly attractive as antibacterial targets, because these enzymes are essential for growth and utilize low-molecular-weight substrates. Using dansylated UDP-MurNAc-tripeptide and L-Ala as the substrates, we established a cell-free assay to measure the sequential reactions of Alr, Ddl and MurF coupled with translocase I. This assay is sensitive and robust enough to screen mixtures of microbial metabolites, and enables us to distinguish the inhibitors for D-Ala–D-Ala formation, MurF and translocase I. D-cycloserine, the D-Ala-D-Ala pathway inhibitor, was successfully detected by this assay (IC50=1.7 μg ml−1). In a large-scale screening of natural products, we have identified inhibitors for D-Ala–D-Ala synthesis pathway, MurF and translocase I.