Crystallization and X-ray diffraction properties of Baeyer-Villiger monooxygenase MtmOIV from the mithramycin biosynthetic pathway in Streptomyces argillaceus.

The Baeyer-Villiger monooxygenase MtmOIV from Streptomyces argillaceus is a 56 kDa FAD-dependent and NADPH-dependent enzyme that is responsible for the key frame-modifying step in the biosynthesis of the natural product mithramycin. Crystals of MtmOIV were flash-cooled and diffracted to 2.69 A resolution using synchrotron radiation on beamline SER-CAT 22-ID at the Advanced Photon Source.

Characterization of kinetics and products of the Baeyer-Villiger oxygenase MtmOIV, the key enzyme of the biosynthetic pathway toward the natural product anticancer drug mithramycin from Streptomyces argillaceus.

MtmOIV, the key oxygenase of the mithramycin biosynthetic pathway in Streptomyces argillaceus, was proven to act initially as Baeyer-Villiger monooxygenase, but may also catalyze various follow-up reaction steps. The reaction of the overexpressed pure His6-tagged enzyme with its substrate premithramycin B was studied. Various intermediates and products were isolated and physicochemically characterized, several of them being previously unknown compounds.

Generation of novel landomycins M and O through targeted gene disruption.

Two genes from Streptomyces cyanogenous S136 that encode the reductase LanZ4 and the hydroxylase LanZ5, which are involved in landomycin A biosynthesis, were characterized by targeted gene inactivation. Analyses of the corresponding mutants as well as complementation experiments have allowed us to show that LanZ4 and LanZ5 are responsible for the unique C-11-hydroxylation that occurs during landomycin biosynthesis. Compounds accumulated by the lanZ4/Z5 mutants are the previously described landomycin F and the new landomycins M and O.

Combining sugar biosynthesis genes for the generation of L- and D-amicetose and formation of two novel antitumor tetracenomycins.

L- and D-stereoisomers of amicetose were generated by combining sugar biosynthesis genes from four different antibiotic gene clusters and both sugars were transferred to the elloramycin aglycone by the sugar flexible ElmGT glycosyltransferase.

Engineering biosynthetic pathways for deoxysugars: branched-chain sugar pathways and derivatives from the antitumor tetracenomycin.

Sugar biosynthesis cassette genes have been used to construct plasmids directing the biosynthesis of branched-chain deoxysugars: pFL942 (NDP-L-mycarose), pFL947 (NDP-4-deacetyl-L-chromose B), and pFL946/pFL954 (NDP-2,3,4-tridemethyl-L-nogalose). Expression of pFL942 and pFL947 in S. lividans 16F4, which harbors genes for elloramycinone biosynthesis and the flexible ElmGT glycosyltransferase of the elloramycin biosynthetic pathway, led to the formation of two compounds: 8-alpha-L-mycarosyl-elloramycinone and 8-demethyl-8-(4-deacetyl)-alpha-L-chromosyl-tetracenomycin C, respectively.