ValC, a New Type of C7-Cyclitol Kinase Involved in the Biosynthesis of the Antifungal Agent Validamycin A

• Published in: Chembiochem : a European journal of chemical biology 2007-04, Vol.8 (6), p.632-641
• Main Authors: Minagawa, Kazuyuki, Zhang, Yirong, Ito, Takuya, Bai, Linquan, Deng, Zixin, Mahmud, Taifo
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Antifungal Agents - biosynthesis; Antifungal Agents - chemistry; biosynthesis; Carbohydrate Sequence; Chemical Phenomena; Chemistry, Physical; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Cloning, Molecular; Cyclins - metabolism; cyclitols; Cyclohexenes - chemistry; Hexosamines - biosynthesis; Hexosamines - chemistry; Inositol - analogs & derivatives; Inositol - biosynthesis; Inositol - chemistry; kinases; Kinetics; Magnetic Resonance Spectroscopy; Mass Spectrometry; Molecular Sequence Data; Phosphotransferases - metabolism; Plasmids - genetics; Recombinant Proteins - biosynthesis; Recombinant Proteins - chemistry; Reverse Transcriptase Polymerase Chain Reaction; Spectrophotometry, Ultraviolet; Streptomyces - enzymology; Streptomyces - genetics; valC; validamycin
• ISSN: 1439-4227; 1439-7633
• DOI: 10.1002/cbic.200600528

The gene valC, which encodes an enzyme homologous to the 2‐epi‐5‐epi‐valiolone kinase (AcbM) of the acarbose biosynthetic pathway, was identified in the validamycin A biosynthetic gene cluster. Inactivation of valC resulted in mutants that lack the ability to produce validamycin A. Complementation experiments with a replicating plasmid harboring full‐length valC restored the production of validamycin A, thus suggesting a critical function of valC in validamycin biosynthesis. In vitro characterization of ValC revealed a new type of C7‐cyclitol kinase, which phosphorylates valienone and validone—but not 2‐epi‐5‐epi‐valiolone, 5‐epi‐valiolone, or glucose—to afford their 7‐phosphate derivatives. The results provide new insights into the activity of this enzyme and also confirm the existence of two different pathways leading to the same end‐product: the valienamine moiety common to acarbose and validamycin A. Two different paths to the same end‐product. A new type of C7‐cyclitol kinase that phosphorylates valienone and validone to afford their 7‐phosphate derivatives has been identified in Streptomyces hygroscopicus var. jinggangensis 5008. The result provides new insights into the activity of this enzyme and its involvement in the biosynthesis of the antifungal agent validamycin A.