Cephalosporin acylase (CA), a member of the N-terminal nucleophile hydrolase family, is activated through sequential primary and secondary autoproteolytic reactions with the release of a pro segment. We have determined crystal structures of four CA mutants. Two mutants are trapped after the primary cleavage, and the other two undergo secondary cleavage slowly. These structures provide a look at...

The reaction mechanism of cytosine deaminase from Escherichia coli is studied using density functional theory. This zinc-dependent enzyme catalyzes the deamination of cytosine to form uracil and ammonia. The calculations give a detailed description of the catalytic mechanism and establish the role of important active-site residues. It is shown that Glu217 is essential for the initial deprotonat...

Nitrile hydratase metalloenzymes are unique and important biocatalysts that are used industrially to produce high value amides from their corresponding nitriles. After more than three decades since their discovery, the mechanism of this class of enzymes is becoming clear with evidence from multiple recent studies that the cysteine-derived sulfenato ligand of the active site metal serves as the ...

Creating efficient artificial catalysts that can compete with biocatalysis has been an enduring challenge which has yet to be met. Reported herein is the synthesis and characterization of a series of zinc complexes designed to catalyze the hydrolysis of phosphate diesters. By introducing a hydrated aldehyde into the ligand we achieve turnover for DNA-like substrates which, combined with ligand ...

The ribosome has an active site comprised of RNA that catalyzes peptide bond formation. To understand how RNA promotes this reaction requires a detailed understanding of the chemical transition state. Here, we report the Brønsted coefficient of the alpha-amino nucleophile with a series of puromycin derivatives. Both 50S subunit- and 70S ribosome-catalyzed reactions displayed linear free-energy ...

By using DABCO·(SO(2))(2), DABSO, as a solid bench-stable SO(2)-equivalent, the palladium-catalysed aminosulfonylation of aryl-, alkenyl- and heteroaryl halides has been achieved. N,N-Dialkylhydrazines are employed as the N-nucleophiles and provide N-aminosulfonamides as the products in good to excellent yields. The reactions are operationally simple to perform, requiring only a slight excess o...

Organic phosphonium salts have served as important intermediates in synthetic chemistry. But the use of a substituent on the positive phosphorus as a nucleophile to construct C-C bond remains a significant challenge. Here we report an efficient transition-metal-free protocol for the direct nucleophilic arylation of carbonyls and imines with tetraarylphosphonium salts in the presence of caesium ...

Group II introns are self-splicing ribozymes that excise themselves from precursor RNAs and catalyze the joining of flanking exons. Excised introns can behave as parasitic RNA molecules: they can catalyze their own insertion into DNA and RNA via a reverse splicing reaction. Previous studies have identified mechanistic roles for various functional groups located in the catalytic core of the intr...

Gold(I)-catalysed direct allylic etherifications have been successfully carried out with chirality transfer to yield enantioenriched, γ-substituted secondary allylic ethers. Our investigations include a full substrate-scope screen to ascertain substituent effects on the regioselectivity, stereoselectivity and efficiency of chirality transfer, as well as control experiments to elucidate the mech...

Solar irradiation including ultraviolet (UV) light causes tissue damage by generating reactive free radicals that can be electrophilic or nucleophilic due to unpaired electrons. Little is known about how free radicals induced by natural sunlight are rapidly detected and avoided by animals. We discover that Drosophila Transient Receptor Potential Ankyrin 1 (TRPA1), previously known only as an el...