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Journal of Bacteriology, July 2003, p. 3962-3965, Vol. 185, No. 13
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.13.3962-3965.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Purification and Characterization of a Monooxygenase Involved in the Biosynthetic Pathway of the Antitumor Drug Mithramycin

Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (I.U.O.P.A.), Universidad de Oviedo, 33006 Oviedo, Spain

Received 13 February 2003/ Accepted 22 April 2003

A monooxygenase encoded by the mtmOIV gene from the mithramycin gene cluster of Streptomyces argillaceus was purified 21-fold by a three-step purification procedure. This monooxygenase catalyzes the oxidative cleavage of the fourth ring of premithramycin B. The enzyme was dependent on NADPH and flavin adenine dinucleotide for activity with optimal pH at 9.5, and the K_m values for NADPH and premithramycin B were 269.22 and 23.35 µM, respectively. The reaction catalyzed by MtmOIV yields two possible isomers of the same basic shortened aliphatic chain molecule. One of the reaction products showed important biological activity, thus highlighting the importance of the cleavage of the fourth ring of the aglycon for biological activity.

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