Characterization of the PLP-dependent aminotransferase NikK from Streptomyces tendae and its putative role in nikkomycin biosynthesis

Alexandra Binter, Gustav Oberdorfer, Sebastian Hofzumahaus, Stefanie Nerstheimer, Georg Altenbacher, Karl Gruber, Peter MacHeroux

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Abstract

As inhibitors of chitin synthase, nikkomycins have attracted interest as potential antibiotics. The biosynthetic pathway to these peptide nucleosides in Streptomyces tendae is only partially known. In order to elucidate the last step of the biosynthesis of the aminohexuronic building block, we have heterologously expressed a predicted aminotransferase encoded by the gene nikK from S. tendae in Escherichia coli. The purified protein, which is essential for nikkomycin biosynthesis, has a pyridoxal-5â-phosphate cofactor bound as a Schiff base to lysine 221. The enzyme possesses aminotransferase activity and uses several standard amino acids as amino group donors with a preference for glutamate (Glu > Phe > Trp > Ala > His > Met > Leu). Therefore, we propose that NikK catalyses the introduction of the amino group into the ketohexuronic acid precursor of nikkomycins. At neutral pH, the UV-visible absorbance spectrum of NikK has two absorbance maxima at 357 and 425 nm indicative of the presence of the deprotonated and protonated aldimine with an estimated pK a of 8.3. The rate of donor substrate deamination is faster at higher pH, indicating that an alkaline environment favours the deamination reaction. Structured digital abstract to by As inhibitors of chitin synthase, nikkomycins have attracted interest as potential antibiotics. However, information on the biosynthetic reactions leading to these peptide nucleosides is still very limited. In order to elucidate the last step of the biosynthesis of the aminohexuronic building block of nikkomycins, we have identified a pyridoxal-5-phosphate dependent aminotransferase

Original languageEnglish
Pages (from-to)4122-4135
Number of pages14
JournalFEBS Journal
Volume278
Issue number21
DOIs
Publication statusPublished - 1 Nov 2011

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Keywords

  • aminohexuronic acid
  • antibiotics
  • docking
  • homology model

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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