We report the structure of a fungal enzyme that activates the amide bond, allowing nucleophilic chemistry.

No abstract

No abstract

Background: It is not clear how the adenylation active site is formed in adenylating enzymes. Results: ATP binding induces adenylate-forming conformation, creates a binding site for the carboxylate substrate, and aligns active site residues for catalysis. Conclusion: ATP configures the adenylation active site. Significance: A new structural role is revealed for ATP in forming the active adenylation conformation in the catalysis of adenylating enzymes.

Escherichia coli is used as a model organism for elucidation of menaquinone biosynthesis, for which a hydrolytic step from 1,4-dihydroxy-2-naphthoyl-coenzyme A (DHNA-CoA) to 1,4-dihydroxy-2-naphthoate is still unaccounted for. Recently, a hotdog fold thioesterase has been shown to catalyze this conversion in phylloquinone biosynthesis, suggesting that its closest homolog, YbgC in Escherichia coli, may be the DHNA-CoA thioesterase in menaquinone biosynthesis. However, this possibility is excluded by the involvement of YbgC in the Tol-Pal system and its complete lack of hydrolytic activity toward DHNA-CoA. To identify the hydrolytic enzyme, we have performed an activity-based screen of all nine Escherichia coli hotdog fold thioesterases and found that YdiI possesses a high level of hydrolytic activity toward DHNA-CoA, with high substrate specificity, and that another thioesterase, EntH, from siderophore biosynthesis exhibits a moderate, much lower DHNA-CoA thioesterase activity. Deletion of the ydiI gene from the bacterial genome results in a significant decrease in menaquinone production, which is little affected in ⌬ybgC and ⌬entH mutants. These results support the notion that YdiI is the DHNA-CoA thioesterase involved in the biosynthesis of menaquinone in the model bacterium.

AgY, CeY, and AgCeY zeolites were successfully prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry−differential thermogravimetry (TG-DTG), and Fourier transform infrared (FT-IR) spectroscopy. The adsorptive desulfurization properties of the adsorbents were evaluated in a fixed-bed unit through different types of model gasoline. The results showed that the AgCeY zeolite has a high desulfurization capacity, similar to that of AgY, and the adsorption affinity for sulfur compounds from model gasoline has the following order: benzothiophene > thiophene. In addition, AgCeY zeolite also has a high selectivity similar to CeY, and the effect on the zeolites for sulfur removal ranks in the following order: pyridine > cyclohexene > toluene. The AgCeY zeolite removes organic sulfur compounds by two types of adsorption modes: π-complexation and direct coordination (S-M) interaction.

Heterocycles, a class of molecules that includes oxazoles, constitute one of the most common building blocks in current pharmaceuticals and are common in medicinally important natural products. The antitumor natural product nataxazole is a model for a large class of benzoxazole‐containing molecules that are made by a pathway that is not characterized. We report structural, biochemical, and chemical evidence that benzoxazole biosynthesis proceeds through an ester generated by an ATP‐dependent adenylating enzyme. The ester rearranges via a tetrahedral hemiorthoamide to yield an amide, which is a shunt product and not, as previously thought, an intermediate in the pathway. A second zinc‐dependent enzyme catalyzes the formation of hemiorthoamide from the ester but, by shuttling protons, the enzyme eliminates water, a reverse hydrolysis reaction, to yield the benzoxazole and avoids the amide. These insights have allowed us to harness the pathway to synthesize a series of novel halogenated benzoxazoles.

No abstract