title: Stereochemical recognition of doubly functional aminotransferase in 2-deoxystreptamine biosynthesis.
abstract: The doubly functional aminotransferase BtrS in the 2-deoxystreptamine (DOS) biosynthesis, in which two transaminations are involved, was characterized by a genetic as well as a chemical approach with the heterologously expressed enzyme. The gene disruption study clearly showed that BtrS is involved, in addition to the previously confirmed first transamination, in the second transamination as well. This dual function of BtrS for the DOS biosynthesis was further confirmed by the structural determination of the reverse reaction product from DOS. Enantiospecific formation of the reverse reaction product from DOS clearly showed that BtrS distinguishes the enantiotopic amino groups of DOS, but in contrast, both enantiomers of 2-deoxy-scyllo-inosose (DOI) were efficiently accepted by BtrS to give a racemic product. This unique stereochemical recognition of DOI chirality and DOS prochirality by BtrS is mechanistically explained by a specific hydrogen-bond donating force in the enzyme active site as a particular feature of this doubly functional enzyme.
authors.affiliation: Department of Chemistry and the Department of Chemistry and Materials Science, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Yokoyama
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Kudo
authors.forename: Mieko
authors.initials: M
authors.lastname: Kuwahara
authors.forename: Kousuke
authors.initials: K
authors.lastname: Inomata
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Tamegai
authors.forename: Tadashi
authors.initials: T
authors.lastname: Eguchi
authors.forename: Katsumi
authors.initials: K
authors.lastname: Kakinuma
mesh_terms: D001407:Bacillus / Q000201:enzymology / Q000235:genetics; D001665:Binding Sites; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005973:Glutamine / Q000378:metabolism; D006595:Hexosamines / Q000096:biosynthesis*; D006860:Hydrogen Bonding; D007294:Inositol / Q000031:analogs & derivatives* / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D013237:Stereoisomerism; D000637:Transaminases / Q000235:genetics / Q000378:metabolism*
chemical_list: D006595:Hexosamines; D011994:Recombinant Proteins; D005973:Glutamine; D007294:Inositol; C075548:2-deoxyinosose; D000637:Transaminases; C007265:2-deoxystreptamine