title: Computational studies on the decarboxylation of 2-(1-carboxy-1-hydroxyethyl)-3,4-dimethylthiazolium dipolar ion, an analog of the complex of pyruvic acid and coenzyme of the pyruvate decarboxylase.
abstract: We have obtained the optimized geometrical structure of 2-(1-carboxy-1-hydroxyethyl)-3,4-dimethylthiazolium dipolar ion and investigated its geometric and electric changes during decarboxylation process by the MNDO-PM3 method, a molecular orbital method. The salient features of the optimized structure are that the dihedral angle of C4-C1-C2-S3 is 5.4 degrees and the distance between thiazolium S3 and carboxyl O6 is about 1.8 A (the bond order between S3 and O6 is about 0.4). The lowest energy decarboxylation profile is the following process. First the dihedral angle of C4-C1-C2-S3 becomes about 90 degrees, then the distance between C1-C2 increases while the dihedral angle holds about 90 degrees, and finally the C1-C2 bond disappears. The most remarkable change caused by the 90 degrees rotation is the disappearance of the S3-O6 bond, and this disappearance causes electric changes that prompt the decarboxylation.
authors.affiliation: Department of Biochemistry, Saitama Medical School, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Y
authors.initials: Y
authors.lastname: Sakagishi
authors.forename: M
authors.initials: M
authors.lastname: Shiibashi
authors.forename: Y
authors.initials: Y
authors.lastname: Suzuki
authors.forename: H
authors.initials: H
authors.lastname: Kato
mesh_terms: D008433:Mathematics; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D011767:Pyruvate Decarboxylase / Q000737:chemistry* / Q000378:metabolism; D011773:Pyruvates / Q000737:chemistry* / Q000378:metabolism; D019289:Pyruvic Acid; D013844:Thiazoles / Q000737:chemistry*
chemical_list: D011773:Pyruvates; D013844:Thiazoles; D019289:Pyruvic Acid; D011767:Pyruvate Decarboxylase