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Site-specific incorporation of a nitrile moiety into proteins which is used as a sensitive infrared probe of local protein environments is demonstrated. The results suggested that thiol alkylation or arylation reaction could easily incorporate various aromatic nitriles into peptides and proteins.

Several electron paramagnetic resonance analyses are conducted to study the mechanisms associated with the biogenesis of high-molecular mass multimeric metalloenzyme nitrile hydratase. A new mechanism for the self-subunit swapping maturation of the compound is also explained.

The article explains various mechanisms that are involved in the catalysis and inhibition of nicotinamidase/pyrazinamidase (PncA) from Mycobacterium tuberculosis. Pyrazinecarbonitrile is shown to be one compound that acts as an irreversible inactivator of PcnA.

Several studies are conducted to explain the 3D structure of the FAD-dependent hydronitrile lyase (HNL) that is obtained from almond with the presence of benzaldehyde in its active site. The reasons behind the absence of the dehydrogenation activity in the cyanohydrin formation mechanism are also discussed.

The studies of the primary and high-pH proton channels in copper nitrite reductase based on high- to atomic-resolution crystal structures are reported. The data obtained indicated that the primary proton channel is not essential for efficient catalysis in Cu nitrite reductase and that the high-pH proton channel is effective for proton transfer and operative at physiological pH values.

The activity-based proteomics and X-ray crystallography are used to identify key active site residues that discriminate small-molecule interactions for the Nit1 and Nit2 nitrilase enzymes. The conservation of nitrilase residues across the vertebrate Nit2 family provide insight into their role in molecular recognition that could be applied to probe substrate binding and selectivity in biological systems.

The catalytic mechanism of Fe-type nitrile hydratases (NHase) is studied by examining the pH and temperature dependence of the kinetic parameters along with the solvent isotope effect for the Fe-type NHase from Comamonas testosteriome Ni1 ([C.sub.t]NHase). The similarities in the kinetic data obtained for both Co- and Fe-type NHase enzyme have shown that both types of NHase enzymes have hydrated nitriles in a similar fashion.

A study was conducted to determine the binding mode of sulfite to the catalytic heme center of pentaheme cytochrome c nitrite reductase (ccNiR) from Wolinella succinogenes at a resolution of 1.7 Angstrom. The observation showed that sulfite and nitrite both provide a pair of electrons to form the coordinative bond to the Fe(III) active site of enzyme while the oxygen atoms of sulfite are found to interact with the three active site protein residues conserved within the enzyme family.