Kunio Isshiki

Inhibition of epidermal growth factor-induced DNA synthesis by tyrosine kinase inhibitors.

We prepared methyl 2,5‐dihydroxycinnamate as a stable analogue of erbstatin, a tyrosine kinase inhibitor. This analogue was about 4 times more stable than erbstatin in calf serum. It inhibited epidermal growth factor receptor‐associated tyrosine kinase in vitro with an IC50 of 0.15 . It also inhibited in situ autophosphorylation of epidermal growth factor receptor in A431 cells. Methyl 2,5‐dihydroxycinnamate was shown to delay the S‐phase induction by epidermal growth factor in quiescent normal rat kidney cells, without affecting the total amount ofDNA synthesis. The effect of erbstatin on S‐phase induction was smaller, possibly because of its shorter life time.

Vanoxonin, a new inhibitor of thymidylate synthetase.

Vanoxonin, a new inhibitor of thymidylate synthetase, was found in cultured broths of the strain MG245-CF2 classified as Saccharopolyspora hirsuta. Vanoxonin, C18H25N3O9, was obtained as colorless powder. Vanoxonin forms a vanadium complex which exhibits a strong inhibition against thymidylate synthetase. The concentration for 50% inhibition of the enzyme (IC50) was 0.7 micrograms/ml.

Asymmetric Reduction of Benzil to (S)-Benzoin with Penicillium claviforme IAM 7294 in a Liquid-Liquid Interface Bioreactor (L-L IBR)

The asymmetric reduction of benzyl to (S)-benzoin with Penicillium claviforme IAM 7294 was applied to a liquid-liquid interface bioreactor (L-L IBR) using a unique polymeric material, ballooned microsphere (MS). The L-L IBR showed superior performance, as compared with suspension, organic-aqueous two-liquid-phase, and solid-liquid interface bioreactor (S-L IBR) systems, affording 14.4 g/l-organic phase of (S)-benzoin (99.0% ee).

A total synthesis of 6-methoxy-epi PS-5 from aminomalonate.

Abstract 6-Methoxy- epi PS-5 1 was stereoselectively synthesized via a bicyclic β-lactam from N-benzyloxycarbonylaminomalonate.

JBIR-17, a novel trichostatin analog from Streptomyces sp. 26634

The Journal of Antibiotics (2009) 62, 283–285; doi:10.1038/ja.2009.22; published online 20 March 2009Keywords: histone deacetylase; histone deacetylase inhibitor; Streptomyces; trichostatinHistone deacetylases (HDACs) play an important role in the epige-netic regulation of gene expression by catalyzing the removal of acetylgroups from lysine residue of histone protein, stimulating chromatincondensation and promoting transcriptional repression.

Generation of new benanomicin analogues by biotransformation using Escherichia coli expressing actinomycete cytochrome P450.

Benanomicins were found as antifungal antibiotics from the culture of an actinomycete with potent antifungal activities in vitro and in vivo. We aimed to generate derivatives superior to benanomicin A by biotransformation using Escherichia coli constructed with bacterial P450 expression system. We found transformation of benanomicin A into two derivatives, 10-hydroxybenanomicin A and 11-O-demethylbenanomicin A by one of the P450-expressed strains which harbored a plasmid carrying a CYP105C1-homologous gene. Unexpectedly, the biotransformed compounds showed weak antifungal activities in vitro compared with those of benanomicin A.

Streptomyces Serine Protease (DHP-A) as a New Biocatalyst Capable of Forming Chiral Intermediates of 1,4-Dihydropyridine Calcium Antagonists

ABSTRACT Streptomyces viridosporus A-914 was screened as a producer of an enzyme to effectively form chiral intermediates of 1,4-dihydropyridine calcium antagonists. The supernatant liquid of the growing culture of this strain exhibited high activity for enantioselective hydrolysis of prochiral 1,4-dihydropyridine diesters to the corresponding (4R) half esters. The responsible enzyme (termed DHP-A) was purified to apparent homogeneity and characterized. Cloning and sequence analysis of the gene for DHP-A (dhpA) revealed that the enzyme was a serine protease that is highly similar in both structural and enzymatic feature to SAM-P45, which is known as a target enzyme of Streptomyces subtilisin inhibitor (SSI), from Streptomyces albogriseolus. In a batch reaction test, DHP-A produced a higher yield of a chiral intermediate of 1,4-dihydropyridine than the commercially available protease P6. Homologous or heterologous expression of dhpA resulted in overproduction of the enzyme in culture supernatants, with 2.4- to 4.2-fold higher specific activities than in the parent S. viridosporus A-914. This indicates that DHP-A is suitable for use in reactions forming chiral intermediates of calcium antagonists and suggests the feasibility of developing DHP-A as a new commercial enzyme for use in the chiral drug industry.

Effect of Cytogenin, a Novel Immunomodulator, on Streptozotocin-induced Diabetes in Mice

The anti-diabetic effect of cytogenin was examined using streptozotocin-induced diabetes in mice. Cytogenin suppressed not only the increase of plasma glucose level but also the body weight reduction in diabetic mice. Histological examination of the pancreas taken from diabetic mice given cytogenin showed that cytogenin decreased the number of macrophages infiltrated into islet of pancreas. Further, cytogenin suppressed the nitric oxide generation by macrophages treated with lipopolysaccharide through decreasing of inducible nitric oxide synthase expression. Cytogenin suppressed interleukin-6 expression by macrophage treated with LPS, suggesting that the anti-diabetic activity of cytogenin might be partly attributed to the suppressive activity against nitric oxide generation.

Practical deracemization of NM-3, a synthetic angiogenesis inhibitor

The practical deracemization of the angiogenesis inhibitor NM-3 is described. The transformation features the diastereoselective addition of optically active pantolactone to a ketene intermediate and hydrolysis of the pantolactone ester.

Structures of OA-6129A, B1, B2 and C, new carbapenem antibiotics

Abstract The structures of carbapenems OA-6129A, B 1 , B 2 and C were determined by spectroscopy and chemical transformation.