Reinvestigation of the metabolite profile in a disruptant of the quinoprotein dehydrogenase (orf23) gene revealed that the Orf23 protein catalyzes dehydrogenation of the C23-C25 lactate moiety to pyruvate during lankacidin biosynthesis in Streptomyces rochei 7434AN4. The dehydrogenase activity was expressed and detected in a soluble fraction of the Streptomyces lividans recombinant harboring orf23. The Orf23 protein preferentially converts lankacidinol to lankacidin C in the presence of pyrroloquinoline quinone (PQQ). Other lankacidinol derivatives, lankacidinol A and iso-lankacidinol, were also converted to the corresponding C-24 keto compounds, lankacidin A (=sedecamycin) and iso-lankacidin C. Addition of various divalent metal cations, especially Ca2+, enhanced the dehydrogenase activity, whereas EDTA completely inhibited. These findings confirmed that the quinoprotein dehydrogenase Orf23 functions at the final oxidation step of lankacidin biosynthesis.
Keywords: Antibiotics; Biosynthesis; Pyrroloquinoline quinone; Quinoprotein dehydrogenase; Secondary metabolite.
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