from P. abyssi consists of a 2-fold symmetric dimer in which each subunit contains 262 residues. Similar to other nitrilases in the nitrilase family, each subunit has an ⍺-β-β-⍺ sandwich fold; when the two subunits come together and interact, the protein forms a ‘super-sandwich’ (⍺-β-β-⍺-⍺-β-β-⍺) structure. In order to dimerize, the C-terminals of each subunit extend out from the core and interact with each other, and this is largely made possible by the salt bridges formed between arginine and glutamate residues. Although the exact binding mechanism to the nitrile substrate still remains unknown, by drawing comparisons between the sequence and structure with other nitrilases, the catalytic triad was determined to consist of Glu 42, Lys 113, and Cys 146. With the aid of protein modeling programs, Glu 42 was observed to be the catalytic base in activating the nucleophile (Cys 146) based on the relatively short distance between the O in Glu and S in Cys. Likewise, Lys 113 was inferred to be the catalytic acid responsible for proton transfer to the substrate. Biological Function Nitrilases have critical roles in plant-microbe interactions for defense, detoxification, nitrogen utilization, and plant hormone synthesis. In plants, there are two distinguishable groups in regard to substrate specificity: those with high hydrolytic activity towards arylacetonitriles and those with high activity towards β-cyano-L-alanine. NIT1, 2, and 3 of the A. thaliana species are examples of the first group of plant nitrilases (arylacetonitrilases) which hydrolyze the nitriles produced during the synthesis or degradation of cyanogenic glycosides and glucosinolates. The arylcetonitrile substrates for these particular enzymes consist of phenylpropionitrile and other products that result from glucosinolate metabolism. NIT4 however, belongs to the second group of plant nitrilases and is critical for cyanide detoxification in plants. Moreover, microbes could also potentially utilize nitrilase for detoxifying and assimilating nitriles and cyanide that exist in the plant environment. An example of this is the β-cyano-L-alanine nitrilase by the plant bacterium P. fluorescens SBW25. Although it is unknown whether this plant bacterium encounters toxic levels of β-cyano-ʟ-alanine in natural settings, nitrilase activity has been observed in cyanogenic plants; thus, it seems that the nitrilase serves as a predominant mechanism for detoxifying cyanide instead of β-cyano-ʟ-alanine. Other bacterial applications of nitrilases produced by plant-associated microorganisms include the degradation of plant nitriles for a carbon and nitrogen source. P. fluorescens EBC191 hydrolyzes many arylacetonitriles, namely mandelonitrile, which serves as a defense against herbivores. Further