Since the isolation of azinomycins A and B in 1954 from the soil bacterium,
Streptomyces sahachiroi, these natural products have been synthetic targets. Both compounds
exhibit in vitro cytotoxic activity at submicromolar levels and demonstrate anti-tumor activities
comparable to that of mitomycin C in vivo. Unique to this class of natural products is the
presence of an aziridine [1,2-a] pyrrolidine ring system. Coupled with an epoxide moiety, these
structural functionalities impart the ability to form interstrand cross-links with DNA via the
electrophilic C10 and C21 carbons of azinomycin and the N7 positions of suitably disposed
purine bases.
This dissertation investigates the global impact of azinomycin B treatment in a yeast
model with special emphasis on DNA damage response, the resulting cell cycle effects, and
cellular localization of the compound. The results provide the first demonstration of the in vivo
actions of azinomycin B and are consistent with the proposed role of the drug as a DNA crosslinking
agent. Biosynthesis of azinomycin B was investigated and appears to have polyketide,
non-ribosomal peptide synthetase and alkaloid origins. In pursuit of elucidating the biosynthetic
origin we developed both a cell culturing system and a cell-free extract procedure capable of
supporting azinomycin synthesis; we used these. These were employed with labeled metabolites
to probe the biosynthetic origins of the molecule. Investigations with this enzyme preparation
imparted important information regarding the substrate and cofactor requirements of the
pathway. These results supported the premise of a mixed origin for the biosynthesis of the
molecule and paved the way for expansive stable isotope labeling studies, which largely revealed
the biosynthetic precursors and probable construction of the azinomycins. Some of these studies
corroborate while other results conflict with initial proposed biosynthetic routes based upon the
azinomycin biosynthetic gene cluster sequence. Future azinomycin biosynthetic gene cluster enzyme characterization, mechanistic
investigations, and genetic modifications will ultimately provide definitive proof for the
intermediacy of proposed biosynthetic precursors and the involvement of specific cofactors.
Better understanding of how nature constructs unique molecule may provide insight into eventual
chemoenzymatic/gene thearapy based approaches toward cancer therapy.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-08-820 |
| Date | 2009 August 1900 |
| Creators | Kelly, Gilbert Thomson |
| Contributors | Watanabe, Coran M. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | application/pdf |
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