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SanM catalyzes the formation of 4-pyridyl-2-oxo-4-hydroxyisovalerate in nikkomycin biosynthesis by interacting with SanN

State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
Biochemical and Biophysical Research Communications (Impact Factor: 2.28). 10/2007; 361(1):196-201. DOI: 10.1016/j.bbrc.2007.07.016
Source: PubMed

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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    • "The peptidyl nucleoside antibiotic nikkomycin, produced by Streptomyces ansochromogenes 7100 [17] and Streptomyces tendae Tü 901 [18], is a promising antibiotic against phytopathogenic fungi and human pathogens. In recent years, considerable progress has been made in understanding nikkomycin biosynthesis [13,17-21]. "
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