title: Characterisation of nitrilase and nitrile hydratase biocatalytic systems.
abstract: Biocatalytic transformations converting aromatic and arylaliphatic nitriles into the analogous related amide or acid were investigated. These studies included synthesis of the beta-substituted nitrile 3-hydroxy-3-phenylpropionitrile, subsequent enrichment and isolation on this substrate of nitrile-degrading microorganisms from the environment, and a comparative study of enzymatic reactions of nitriles by resting cell cultures and enzymes. Each biocatalyst exhibited a distinctive substrate selectivity profile, generally related to the length of the aliphatic chain of the arylaliphatic nitrile and the position of substituents on the aromatic ring or aliphatic chain. Cell-free nitrilases generally exhibited a narrower substrate range than resting whole cells of Rhodococcus strains. The Rhodococcus strains all exhibited nitrile hydratase activity and converted beta-hydroxy nitriles (but did not demonstrate enantioselectivity on this substrate). The biocatalysts also mediated the synthesis of a range of alpha-hydroxy carboxylic acids or amides from aldehydes in the presence of cyanide. The use of an amidase inhibitor permits halting the nitrile hydratase/amidase reaction at the amide intermediate.
authors.affiliation: CSIR Bio/Chemtek, Modderfontein 1645, Private Bag X2 Johannesburg, South Africa. dbrady@csir.co.za
authors.forename: D
authors.initials: D
authors.lastname: Brady
authors.forename: A
authors.initials: A
authors.lastname: Beeton
authors.forename: J
authors.initials: J
authors.lastname: Zeevaart
authors.forename: C
authors.initials: C
authors.lastname: Kgaje
authors.forename: F
authors.initials: F
authors.lastname: van Rantwijk
authors.forename: R A
authors.initials: RA
authors.lastname: Sheldon
mesh_terms: D000079:Acetaldehyde / Q000031:analogs & derivatives* / Q000378:metabolism; D000581:Amidohydrolases / Q000378:metabolism; D000619:Aminohydrolases / Q000302:isolation & purification / Q000378:metabolism*; D001407:Bacillus / Q000201:enzymology / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D001419:Bacteria / Q000201:enzymology* / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism; D001711:Biotransformation; D002264:Carboxylic Acids / Q000378:metabolism; D002384:Catalysis; D002474:Cell-Free System / Q000378:metabolism; D006836:Hydro-Lyases / Q000302:isolation & purification / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D015394:Molecular Structure; D009570:Nitriles / Q000737:chemistry / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D012240:Rhodococcus / Q000201:enzymology / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D012988:Soil Microbiology; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D002264:Carboxylic Acids; D009570:Nitriles; D000581:Amidohydrolases; C019665:amidase; D000619:Aminohydrolases; C021867:nitrilase; D006836:Hydro-Lyases; C048831:nitrile hydratase; D000079:Acetaldehyde; C013192:phenylacetaldehyde