Glucomannan synthesis in pea epicotyls: the mannose and glucose transferases

Planta. 1993;190(2):206-20. doi: 10.1007/BF00196613.


Membrane fractions and digitonin-solubilized enzymes prepared from stem segments isolated from the third internode of etiolated pea seedlings (Pisum sativum L. cv. Alaska) catalyzed the synthesis of a beta-1,4-[14C]mannan from GDP-D-[U-14C]-mannose, a mixed beta-1,3- and beta-1,4-[14C]glucan from GDP-D-[U-14C]-glucose and a beta-1,4-[14C]-glucomannan from both GDP-D-[U-14C]mannose and GDP-D-[U-14C]glucose. The kinetics of the membrane-bound and soluble mannan and glucan synthases were determined. The effects of ions, chelators, inhibitors of lipid-linked saccharides, polyamines, polyols, nucleotides, nucleoside-diphosphate sugars, acetyl-CoA, group-specific chemical probes, phospholipases and detergents on the membrane-bound mannan and glucan synthases were investigated. The beta-glucan synthase had different properties from other preparations which bring about the synthesis of beta-1,3-glucans (callose) and mixed beta-1,3- and beta-1,4- glucans and which use UDP-D-glucose as substrate. It also differed from xyloglucan synthase because in the presence of several concentrations of UDP-D-xylose in addition to GDP-D-glucose no xyloglucan was formed. Using either the membrane-bound or the soluble mannan synthase, GDP-D-glucose acted competitively in the presence of GDP-D-mannose to inhibit the incorporation of mannose into the polymer. This was not due to an inhibition of the transferase activity but was a result of the incorporation of glucose residues from GDP-D-glucose into a glucomannan. The kinetics and the composition of the synthesized glucomannan depended on the ratio of the concentrations of GDP-D-glucose and GDP-D-mannose that were available. Our data indicated that a single enzyme has an active centre that can use both GDP-D-mannose and GDP-D-glucose to bring about the synthesis of the heteropolysaccharide.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetyl Coenzyme A / pharmacology
  • Carbohydrate Sequence
  • Carbohydrates / pharmacology
  • Cations, Divalent / metabolism
  • Digitonin
  • Fabaceae / enzymology
  • Fabaceae / metabolism*
  • Glucans / biosynthesis
  • Glucosyltransferases / metabolism*
  • Guanosine Diphosphate Mannose / metabolism
  • Guanosine Diphosphate Sugars / metabolism
  • Kinetics
  • Mannans / biosynthesis*
  • Mannosyltransferases / metabolism*
  • Membranes / enzymology
  • Molecular Sequence Data
  • Nucleotides / pharmacology
  • Plants, Medicinal*
  • Spermine / pharmacology
  • Uridine Diphosphate Glucose / pharmacology
  • Uridine Diphosphate Xylose / pharmacology


  • Carbohydrates
  • Cations, Divalent
  • Glucans
  • Guanosine Diphosphate Sugars
  • Mannans
  • Nucleotides
  • beta-1,4-mannan
  • Spermine
  • Guanosine Diphosphate Mannose
  • Uridine Diphosphate Xylose
  • guanosine diphosphate glucose
  • Acetyl Coenzyme A
  • Glucosyltransferases
  • Mannosyltransferases
  • mannan synthetase
  • Digitonin
  • Uridine Diphosphate Glucose