Dextran acceptor reaction of Streptococcus sobrinus glucosyltransferase GTF-I as revealed by using uniformly 13C-labeled sucrose.
A sucrose glucosyltransferase GTF-I from cariogenic Streptococcus sobrinus transferred the uniformly 13C-labeled glucosyl residue ([U-(13)C]Glc) from [U-(13)C]sucrose to exogenous dextran T500 at the non-reducing-end, mostly by alpha-(1-->6) linkages and partially by alpha-(1-->3) linkages, as revealed by the 13C-(13)C NMR coupling pattern. With increasing amounts of [U-(13)C]sucrose, transfer of [U-(13)C]Glc to the alpha-(1-->3)-linked chain became predominant without increase in the number of chains. The transfer of [U-(13)C]Glc to an isomaltopentaose acceptor occurred similarly to its transfer to T500. alpha-(1-->3)-branches in the [U-(13)C]dextran, specifically synthesized from [U-(13)C]sucrose by a Streptococcus bovis dextransucrase, were not formed by GTF-I, as judged by the observation that a newly-formed alpha-1,3,6-branched [U-(13)C]Glc was not detected, which could have been formed by transferring the unlabeled Glc from sucrose to the internal alpha-(1-->6)-linked [U-(13)C]Glc at C-3. The 13C-(13)C one-bond coupling constants (1J) were also recorded for the C-1--C-6 bond of the internal alpha-(1-->6)-linked [U-(13)C]Glc and of the non-reducing-end [U-(13)C]Glc.
Mukasa
H
H
Department of Chemistry, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan. hmukasa@cc.ndmc.ac.jp
Tsumori
H
H
Shimamura
A
A
D001426:Bacterial Proteins; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002247:Carbon Isotopes; D003911:Dextrans / Q000737:chemistry / Q000378:metabolism*; D005964:Glucosyltransferases / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D016986:Streptococcus sobrinus / Q000201:enzymology*; D013379:Substrate Specificity; D013395:Sucrose / Q000737:chemistry / Q000378:metabolism
D001426:Bacterial Proteins; D002247:Carbon Isotopes; D003911:Dextrans; D009844:Oligosaccharides; D011506:Proteins; C067118:GTF-I protein, Streptococcus; D013395:Sucrose; D005964:Glucosyltransferases; C489364:glucosyltransferase I