Rapid generation of hydrogen peroxide contributes to the complex cell death induction by the angucycline antibiotic landomycin E.

Landomycin E (LE) is an angucycline antibiotic produced by Streptomyces globisporus. Previously, we have shown a broad anticancer activity of LE which is, in contrast to the structurally related and clinically used anthracycline doxorubicin (Dx), only mildly affected by multidrug resistance-mediated drug efflux. In the present study, cellular and molecular mechanisms underlying the anticancer activity of landomycin E towards Jurkat T-cell leukemia cells were dissected focusing on the involvement of radical oxygen species (ROS).

Molecular insight into substrate recognition and catalysis of Baeyer-Villiger monooxygenase MtmOIV, the key frame-modifying enzyme in the biosynthesis of anticancer agent mithramycin.

Baeyer-Villiger monooxygenases (BVMOs) have been shown to play key roles for the biosynthesis of important natural products. MtmOIV, a homodimeric FAD- and NADPH-dependent BVMO, catalyzes the key frame-modifying steps of the mithramycin biosynthetic pathway, including an oxidative C-C bond cleavage, by converting its natural substrate premithramycin B into mithramycin DK, the immediate precursor of mithramycin. The drastically improved protein structure of MtmOIV along with the high-resolution structure of MtmOIV in complex with its natural substrate premithramycin B are reported here, revealing previously undetected key residues that are important for substrate recognition and catalysis.

Baeyer-Villiger C-C bond cleavage reaction in gilvocarcin and jadomycin biosynthesis.

GilOII has been unambiguously identified as the key enzyme performing the crucial C-C bond cleavage reaction responsible for the unique rearrangement of a benz[a]anthracene skeleton to the benzo[d]naphthopyranone backbone typical of the gilvocarcin-type natural anticancer antibiotics. Further investigations of this enzyme led to the isolation of a hydroxyoxepinone intermediate, leading to important conclusions regarding the cleavage mechanism.

Roles of the synergistic reductive O-methyltransferase GilM and of O-methyltransferase GilMT in the gilvocarcin biosynthetic pathway.

Two enzymes of the gilvocarcin biosynthetic pathway, GilMT and GilM, with unclear functions were investigated by in vitro studies using purified, recombinant enzymes along with synthetically prepared intermediates. The studies revealed GilMT as a typical S-adenosylmethionine (SAM) dependent O-methyltransferase, but GilM was identified as a pivotal enzyme in the pathway that exhibits dual functionality in that it catalyzes a reduction of a quinone intermediate to a hydroquinone, which goes hand-in-hand with a stabilizing O-methylation and a hemiacetal formation. GilM mediates its reductive catalysis through the aid of GilR that provides FADH(2) for the GilM reaction, through which FAD is regenerated for the next catalytic cycle.