Stigmatella aurantiaca Sg a15 carries genes encoding type I and type II 3-deoxy- d - arabino -heptulosonate-7-phosphate
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O R I G I N A L PA P E R
Barbara Silakowski · Brigitte Kunze · Rolf Müller
Stigmatella aurantiaca Sg a15 carries genes encoding type I and type II 3-deoxy-D-arabino-heptulosonate-7-phosphate synthases: involvement of a type II synthase in aurachin biosynthesis Received: 20 January 2000 / Revised: 15 March 2000 / Accepted: 21 March 2000 / Published online: 14 April 2000 © Springer-Verlag 2000
Abstract 3-Deoxy- D -arabino-heptulosonate-7-phosphate (DAHP) synthases catalyse the first step of the shikimate pathway. Two unrelated DAHP synthase types have been described in plants and bacteria. Two type II (aroAA2 and aroAA5) and one type I DAHP synthase gene (aroA001) were identified from the myxobacterium Stigmatella aurantiaca Sg a15. Inactivation of aroAA5 leads to a mutant that is impaired in the biosynthesis of aurachins, which are electron transport inhibitors and contain an anthranilate moiety. Feeding of anthranilic acid to the mutant culture restores production of aurachins. Inactivation of aroAA2 and aroA001 does not impair production of aurachins or other known secondary metabolites of S. aurantiaca Sg a15. Key words Myxobacteria · Stigmatella aurantiaca · Aurachin · Secondary metabolism · 3-Deoxy-D-arabinoheptulosonate-7-phosphate synthases Abbreviations DAHP 3-Deoxy-D-arabinoheptulosonate-7-phosphate · NRPS Non-ribosomal peptide synthetase · PKS Polyketide synthase
B. Silakowski · R. Müller (✉) Gesellschaft für Biotechnologische Forschung (GBF), Department NBi/MX, Mascheroder Weg 1, 38124 Braunschweig, Germany e-mail: [email protected], Tel.: +49-531-6181420, Fax: +49-531-6181284 B. Kunze Gesellschaft für Biotechnologische Forschung (GBF), Department NBI, Mascheroder Weg 1, 38124 Braunschweig, Germany R. Müller Institut für Pharmazeutische Biologie, TU Braunschweig, Mendelssohnstrasse 1, 38106 Braunschweig, Germany
Introduction Microorganisms and plants use the seven-step shikimate pathway for the biosynthesis of chorismate, which serves as the metabolic precursor of aromatic amino acids, vitamins E and K, folic acid, ubiquinone, menaquinone, enterobactin and a variety of secondary metabolites (Bentley 1990; Haslam 1993). In the first step of the pathway 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase (EC 4.1.2.15) catalyses the condensation of phosphoenolpyruvate and erythrose 4-phosphate to form DAHP. Diverse mechanisms controlling the carbon flow through the shikimate pathway have been described for DAHP synthases from a variety of organisms and involve modulation of enzyme activity by feedback inhibition or transcriptional regulation (Bentley 1990). Microorganisms have been shown to possess up to three different DAHP synthase isoenzymes. The nucleotide sequences of the encoding genes are very similar. A type I DAHP synthase consensus sequence has been defined and is available at the Protein families database (Pfam) of the Sanger Centre (URL: http:www.sanger.ac. uk/Software/Pfam). A second class of DAHP synthases (type II) not related to the microbial enzymes was formerly thought to be present onl
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