ABSTRACT
The biosynthesis of the azinomycins involves the conversion of glutamic acid to an aziridino[1,2-a]pyrrolidine moiety, which together with the epoxide moiety imparts anticancer activity to these agents. The mechanism of azabicycle formation is complex and involves at least 14 enzymatic steps. Previous research has identified N-acetyl-glutamate 5-semialdehyde as a key intermediate, which originates from protection of the amino terminus of glutamic acid and subsequent reduction of the γ-carboxylate. This study reports on the seminal discovery of a thiamin-dependent transketolase responsible for the formation of 2-acetamido-5,6-dihydroxy-6-oxoheptanoic acid, which accounts for the two-carbon extension needed to complete the carbon framework of the azabicycle moiety.
Subject(s)
Azabicyclo Compounds/chemistry , Azabicyclo Compounds/metabolism , Transketolase/metabolism , Humans , Models, Molecular , Protein Conformation , Transketolase/chemistryABSTRACT
The azinomycins are potent antitumor agents produced by the soil bacterium Streptomyces sahachiroi and contain a novel aziridino[1,2-a]pyrrolidine core; its synthesis involves at least 14 steps. This study reports the first reconstitution of N-acetylglutamine semialdehyde formation by two enzymes encoded in the azinomycin biosynthetic gene cluster. The reaction proceeds through the formation of an acylphosphate and establishes N-acetyl-glutamyl 5-phosphate and N-acetylglutamine semialdehyde as intermediates in the complex biosynthesis of the aziridino[1,2-a]pyrrolidine moiety.
Subject(s)
Biosynthetic Pathways , Glutamates/metabolism , Antineoplastic Agents/metabolism , Azabicyclo Compounds , Bacterial Proteins/chemistry , Bacterial Proteins/physiology , Catalytic Domain , Dipeptides , Glycopeptides/biosynthesis , Intercellular Signaling Peptides and Proteins , Kinetics , Naphthalenes/metabolism , Peptides/metabolism , Streptomyces/enzymology , Streptomyces/geneticsABSTRACT
BACKGROUND: Limited data exist about the use, efficacy, and prognostic factors influencing outcome when CyberKnife is used to treat dogs with intracranial neoplasia. OBJECTIVES: To determine the prognosis and associated prognostic factors for dogs that were imaged, determined to have primary intracranial tumors, and treated with CyberKnife radiotherapy. ANIMALS: Fifty-nine dogs treated with CyberKnife radiotherapy for primary intracranial tumors. METHODS: Retrospective medical record review of cases from January 2010 to June 2016. Data extracted from medical records included signalment, weight, seizure history, tumor location, tumor type (based on imaging), gross tumor volume, planned tumor volume, treatment dates, radiation dose, recurrence, date of death, and cause of death. RESULTS: The median progression-free interval (PFI) was 347 days (range 47 to 1529 days), and the median survival time (MST) was 738 days (range 4 to 2079 days). Tumor location was significantly associated with PFI when comparing cerebrum (median PFI 357 days; range 47-1529 days) versus cerebellum (median PFI 97 days; range 97-168 days) versus brainstem (median PFI 266 days; range 30-1484 days), P = .03. Additionally, the presumed tumor type was significantly associated with MST (P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE: Use of Cyberknife and SRT might improve MST, compared with RT, in dogs with intracranial neoplasia.