Extent of β-glucan chain elongation by ryegrass (Lolium multiflorum) enzymes

The chain length and linkage composition of water-soluble β-glucans produced in vitro from UDP-¹⁴C] glucose by ryegrass membranes was determined by methylation analysis. The methylated β-glucans were acid-hydrolysed and the partially methylated sugar products reduced to the corresponding methylated alditols. Mass spectra were recorded for the permethylated alditols following their separation by reversed-phase h.p.l.c. 64% of the radiolabelled β-glucosyl residues were 3-substituted, 33% were 4-substituted and 3% were non-reducing terminal residues indicating that the average degree of polymerization of the radiolabelled sequences was 33. This result demonstrates that substantial elongation of β-glucan chains was occurring in vitro and that chain elongation was from the non-reducing end.