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      Recent development of two chitinase inhibitors, Argifin and Argadin, produced by soil microorganisms

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          Abstract

          Chitin, the second most abundant polysaccharide in nature, occurs in fungi, some algae and many invertebrates, including insects. Thus, chitin synthesis and degradation could represent specific targets for fungicides and insecticides. Chitinases hydrolyze chitin into oligomers of N-acetyl- d-glucosamine at key points in the life cycles of organisms, consequently, chitinase inhibitors have become subject of increasing interest. This review covers the development of two chitinase inhibitors of natural origin, Argifin and Argadin, isolated from the cultured broth of microorganisms in our laboratory. In particular, the practical total synthesis of these natural products, the synthesis of lead compounds via computer-aided rational molecular design, and discovery methods that generate only highly-active compounds using a kinetic target(chitinase)-guided synthesis approach (termed in situ click chemistry) are described.

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          Most cited references44

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          New families in the classification of glycosyl hydrolases based on amino acid sequence similarities.

          301 glycosyl hydrolases and related enzymes corresponding to 39 EC entries of the I.U.B. classification system have been classified into 35 families on the basis of amino-acid-sequence similarities [Henrissat (1991) Biochem. J. 280, 309-316]. Approximately half of the families were found to be monospecific (containing only one EC number), whereas the other half were found to be polyspecific (containing at least two EC numbers). A > 60% increase in sequence data for glycosyl hydrolases (181 additional enzymes or enzyme domains sequences have since become available) allowed us to update the classification not only by the addition of more members to already identified families, but also by the finding of ten new families. On the basis of a comparison of 482 sequences corresponding to 52 EC entries, 45 families, out of which 22 are polyspecific, can now be defined. This classification has been implemented in the SWISS-PROT protein sequence data bank.
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            Acidic mammalian chitinase in asthmatic Th2 inflammation and IL-13 pathway activation.

            Chitin is a surface component of parasites and insects, and chitinases are induced in lower life forms during infections with these agents. Although chitin itself does not exist in humans, chitinases are present in the human genome. We show here that acidic mammalian chitinase (AMCase) is induced via a T helper-2 (Th2)-specific, interleukin-13 (IL-13)-mediated pathway in epithelial cells and macrophages in an aeroallergen asthma model and expressed in exaggerated quantities in human asthma. AMCase neutralization ameliorated Th2 inflammation and airway hyperresponsiveness, in part by inhibiting IL-13 pathway activation and chemokine induction. AMCase may thus be an important mediator of IL-13-induced responses in Th2-dominated disorders such as asthma.
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              Ruthenium-catalyzed azide-alkyne cycloaddition: scope and mechanism.

              The catalytic activity of a series of ruthenium(II) complexes in azide-alkyne cycloadditions has been evaluated. The [Cp*RuCl] complexes, such as Cp*RuCl(PPh 3) 2, Cp*RuCl(COD), and Cp*RuCl(NBD), were among the most effective catalysts. In the presence of catalytic Cp*RuCl(PPh 3) 2 or Cp*RuCl(COD), primary and secondary azides react with a broad range of terminal alkynes containing a range of functionalities selectively producing 1,5-disubstituted 1,2,3-triazoles; tertiary azides were significantly less reactive. Both complexes also promote the cycloaddition reactions of organic azides with internal alkynes, providing access to fully-substituted 1,2,3-triazoles. The ruthenium-catalyzed azide-alkyne cycloaddition (RuAAC) appears to proceed via oxidative coupling of the azide and alkyne reactants to give a six-membered ruthenacycle intermediate, in which the first new carbon-nitrogen bond is formed between the more electronegative carbon of the alkyne and the terminal, electrophilic nitrogen of the azide. This step is followed by reductive elimination, which forms the triazole product. DFT calculations support this mechanistic proposal and indicate that the reductive elimination step is rate-determining.
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                Author and article information

                Journal
                Proc Jpn Acad Ser B Phys Biol Sci
                Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci
                PJAB
                Proceedings of the Japan Academy. Series B, Physical and Biological Sciences
                The Japan Academy (Tokyo, Japan )
                0386-2208
                1349-2896
                February 2010
                : 86
                : 2
                : 85-102
                Affiliations
                [*1 ]The Kitasato Institute, Kitasato Institute for Life Sciences and Graduate School of Infection Control Sciences, Kitasato University, Tokyo, Japan
                Author notes
                []Correspondence should be addressed: T. Sunazuka and S. Ōmura, The Kitasato Institute and Kitasato Institute for Life Science and Graduate School of Infection Control Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan (e-mail: sunazuka@ 123456lisci.kitasato-u.ac.jp and omuras@ 123456insti.kitasato-u.ac.jp ).

                Contributed by Satoshi Ō mura, m.j.a.

                Article
                pjab-86-085
                10.2183/pjab.86.85
                3417560
                20154467
                7a4f566c-99a4-43c6-ba6d-d0a0c77e5f03
                © 2010 The Japan Academy

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 07 December 2009
                : 07 January 2010
                Categories
                Review

                Life sciences
                argadin,solid-phase synthesis,argifin,in situ click chemistry,rational molecular design,chitinase inhibitor

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