title: Substrate profiling of cyclohexylamine oxidase and its mutants reveals new biocatalytic potential in deracemization of racemic amines.
abstract: A cyclohexylamine oxidase (CHAO) of bacterial origin was previously shown to be a potentially useful catalyst in the deracemization of racemic primary amines. To further explore the properties and application of this enzyme, five single-amino acid substitution mutants (L199A, M226A, Y321A, Y321F, and L353M) were created based on superimposition of the tertiary structure of CHAO and the monoamine oxidase (MAO) B homolog. The substrate specificity of the purified wild-type and five mutant enzymes were examined towards 38 structurally diverse amines. All the enzymes exhibited better activity for primary amines than secondary and tertiary amines and in general exhibited high stereoselectivity. Among the mutant enzymes, M226A displayed an enhanced activity (5-400%) towards most substrates, and L353M showed 7-445% higher activity towards primary aliphatic amines with cycloalkane or aromatic moieties. Kinetic parameters revealed that both Y321 mutants showed higher catalytic efficiency towards cyclooctanamine, whereas the wild-type CHAO (wt CHAO) was most efficient towards cyclohexylamine. The wt CHAO or variant L353M in combination with a borane-ammonia complex as reducing agent was applied to the deracemization of 1-aminotetraline to give the (R)-enantiomer, a precursor of an antidepressant drug Norsertraline, in good yield (73-76%), demonstrating their application potential in chiral amine synthesis.
authors.affiliation: National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 Xi Qi Dao, Tianjin Airport Economic Area, Tianjin, 300308, People's Republic of China.
authors.forename: Guangyue
authors.initials: G
authors.lastname: Li
authors.forename: Jie
authors.initials: J
authors.lastname: Ren
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Iwaki
authors.forename: Dalong
authors.initials: D
authors.lastname: Zhang
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Hasegawa
authors.forename: Qiaqing
authors.initials: Q
authors.lastname: Wu
authors.forename: Jinhui
authors.initials: J
authors.lastname: Feng
authors.forename: Peter C K
authors.initials: PC
authors.lastname: Lau
authors.forename: Dunming
authors.initials: D
authors.lastname: Zhu
mesh_terms: D000588:Amines / Q000737:chemistry / Q000378:metabolism*; D055162:Biocatalysis; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000378:metabolism*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D000588:Amines; C019962:cyclohexylamine oxidase; D000587:Oxidoreductases Acting on CH-NH Group Donors