SanM catalyzes the formation of 4-pyridyl-2-oxo-4-hydroxyisovalerate in nikkomycin biosynthesis by interacting with SanN.
ABSTRACT Nikkomycins are peptidyl nucleoside antibiotics with potent activities against phytopathogenic and human pathogenic fungi. The sanM and sanN genes are required for the nikkomycin biosynthesis of Streptomyces ansochromogenes. In the present study, interaction between SanM and SanN was identified by yeast two-hybrid and co-immunoprecipitation assays. Moreover, SanM and SanN were heterologously expressed and purified. Further biochemical assay demonstrated that the SanM-SanN interaction is essential for SanM aldolase activity but not for SanN dehydrogenase activity. SanM converts piconaldehyde and 2-oxobutyrate to 4-pyridyl-2-oxo-4-hydroxyisovalerate in nikkomycin biosynthesis by interacting with SanN. Steady state kinetics analysis revealed that K(m) and k(cat)/K(m) of SanM are 123.2 microM and 11.4 mM(-1)s(-1) for picolinaldehyde, while 335.6 microM and 4.0 mM(-1)s(-1) for 2-oxobutyrate, respectively. However, SanN as a dehydrogenase is independent of SanM.
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ABSTRACT: Carbon‐carbon bond formation is among the most challenging transformations in the organic synthetic chemistry. Enzymes capable to perform this reaction are of great interest. The enzymes for stereoselective CC bond formations have been investigated very intensively during the last two decades. New recombinant DNA technologies have paved the way for improved catalysts and broaden the application scope of the already known enzymes and reactions. On the other side new discoveries have brought more enzyme players in the arena of CC bond formation reactions. Novel enzymatic CC bond formation reactions have been applied, implying the most important benefit of biocatalysis, namely the high selectivity.ChemCatChem 06/2013; 5(6). DOI:10.1002/cctc.201200709 · 5.04 Impact Factor
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ABSTRACT: The term "adaptation" in the behavioral sciences refers to the ability of living tissue to adjust to the demands of environmental changes. This is accomplished in a variety of ways. For example, the sense organs become less sensitive when stimulated and more sensitive when stimulation is removed. Long-term effects of adaptation, for example to distracting noises, are observed in the absence of known physiological changes. The perceptual system is able to extract from the large quantity and quality of stimuli impinging upon it only those which are of interest and relevance. The prime mechanism of adaptation, however, is the ability of the human operator to adjust his responses to novel situations, i.e., learning It is the redundancy of the human operator which is his most valuable asset and prescribes the inclusion of the human in complex systems in spite of the concomitant demands for life support. The papers in the symposium are designed to illustrate several ways in which the human operator exhibits adaptation.
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ABSTRACT: In this paper, a recombinant trans-o-hydroxybenzylidenepyruvate hydratase-aldolase (tHBP-HA) of Pseudomonas fluorescens N3 was used as a new catalyst for aldol condensation reactions. The reaction of some aldehydes with a different electronic activation catalyzed by tHBP-HA is presented and discussed together with some hints on the product structure. The enzyme is strictly pyruvate-dependent but uses different aldehydes as acceptors. The structure of the products is highly dependent on the electronic characteristics of the aldehyde. The results are interesting for both their synthetic importance and the mechanism of the formation of the products. Not only the products obtained and the recognition power are reported, but also some characteristics of its mechanism are analyzed. The results clearly show that the enzyme is efficiently prepared, purified, and stored, that it recognizes many different substrates, and that the products depend on the substrate electronic nature.Applied biochemistry and biotechnology 05/2013; DOI:10.1007/s12010-013-0302-3 · 1.69 Impact Factor