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A new isochorismate synthase specifically involved in menaquinone (vitamin K2) biosynthesis encoded by the menF gene

R. Daruwala, O. Kwon, R. Meganathan, M.E.S. Hudspeth
DOI: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08330.x 159-163 First published online: 1 July 1996

Abstract

A new gene (menF) encoding an isochorismate synthase specifically involved in menaquinone (vitamin K2) biosynthesis has been cloned and sequenced. Overexpression of the encoded polypeptide under the influence of a T7 promoter showed an increase in specific activity of 2200-fold. Treatment with protamine sulfate resulted in another 3.5-fold increase in specific activity (7700-fold compared to the parent strain). The relative molecular mass of the overexpressed protein was Mr 49 000, which is in full agreement with the DNA sequence predicted molecular mass of 48777 Da. Purified enzyme converted chorismate to isochorismate with the product of the reaction shown to be isochorismate by its thermal conversion to salicylic acid. The fluorescence spectrum generated by the formed salicylic acid was identical to that of authentic salicylic acid. The 5′ end of the flanking menD gene has also been redefined.

Keywords
  • Isochorismate synthase
  • Menaquinone biosynthesis
  • menF gene