Lipid-linked intermediates are involved in the synthesis of the exopolysaccharide xanthan produced by the bacterium Xanthomonas campestris (L. Ielpi, R. O. Couso, and M. A. Dankert, FEBS Lett. 130:253-256, 1981). In this study, the stepwise assembly of the repeating pentasaccharide unit of xanthan is described. EDTA-treated X. campestris cells were used as both enzyme preparation and lipid-P acceptor, and UDP-Glc, GDP-Man, and UDP- glucuronic acid were used as sugar donors. A linear pentasaccharide unit is assembled on a polyprenol-P lipid carrier by the sequential addition of glucose-1-P, glucose, mannose, glucuronic acid, and mannose. The in vitro synthesis of pentasaccharide-P-P-polyprenol was also accompanied by the incorporation of radioactivity into a polymeric product, which was characterized as xanthan, on the basis of gel filtration and permethylation studies. Results from two-stage reactions showed that essentially pentasaccharide-P-P-polyprenol is polymerized. In addition, the direction of chain elongation has been studied by in vivo experiments. The polymerization of lipid-linked repeat units occurs by the successive transfer of the growing chain to a new pentasaccharide-P-P-polyprenol. The reaction involves C-1 of glucose at the reducing end of the polyprenol-linked growing chain and C-4 of glucose at the nonreducing position of the newly formed polyprenol-linked pentasaccharide, generating a branched polymer with a trisaccharide side chain.
Documento: | Artículo |
Título: | Sequential assembly and polymerization of the polyprenol-linked pentasaccharide repeating unit of the xanthan polysaccharide in Xanthomonas campestris |
Autor: | Ielpi, L.; Couso, R.O.; Dankert, M.A. |
Filiación: | IIBFC, Facultad Ciencias Exactas/Naturales, CNICT, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina |
Palabras clave: | glucose; glucose 1 phosphate; glucuronic acid; guanosine diphosphate; lipid; mannose; pentasaccharide; polyprenoic acid; uridine diphosphate glucose; uridine diphosphate glucuronic acid; xanthan; article; carbohydrate synthesis; gel filtration; methylation; nonhuman; polymerization; priority journal; Xanthomonas; Bacteria (microorganisms); Xanthomonas campestris |
Año: | 1993 |
Volumen: | 175 |
Número: | 9 |
Página de inicio: | 2490 |
Página de fin: | 2500 |
DOI: | http://dx.doi.org/10.1128/jb.175.9.2490-2500.1993 |
Título revista: | Journal of Bacteriology |
Título revista abreviado: | J. BACTERIOL. |
ISSN: | 00219193 |
CODEN: | JOBAA |
CAS: | glucose, 50-99-7, 84778-64-3; glucose 1 phosphate, 59-56-3; glucuronic acid, 36116-79-7, 576-37-4, 6556-12-3; guanosine diphosphate, 146-91-8; lipid, 66455-18-3; mannose, 31103-86-3, 3458-28-4; uridine diphosphate glucose, 133-89-1; uridine diphosphate glucuronic acid, 2616-64-0; xanthan, 11138-66-2 |
Registro: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00219193_v175_n9_p2490_Ielpi |