Zusammenfassung
The bulbs of Lilium testaceum contain large quantities of a storage β-1,4-glucomannan (β-1,4-GM) with a Man to Glc ratio of 7 to 3 and a Mr of 230 000. The mobilization of the β-1,4-GM as well as of the accompanying starch proceeds during germination of the Lilium bulbs. Enzymes responsible for the breakdown of the reserve polysaccharides were shown to be α-amylase, α-glucosidase, β-mannosidase, ...
Zusammenfassung
The bulbs of Lilium testaceum contain large quantities of a storage β-1,4-glucomannan (β-1,4-GM) with a Man to Glc ratio of 7 to 3 and a Mr of 230 000. The mobilization of the β-1,4-GM as well as of the accompanying starch proceeds during germination of the Lilium bulbs. Enzymes responsible for the breakdown of the reserve polysaccharides were shown to be α-amylase, α-glucosidase, β-mannosidase, β-glucosidase and endo-β-mannanase. A crude enzyme preparation hydrolysing the Lilium GM was isolated from germinated Lilium bulbs and enzymes were separated by ion exchange chromatography (IEC) on DEAE-Sephacel and by gel permeation chromatography (GPC) on Superose™12. The purified β-mannanase exhibited optimal activity at pH 4.5 and an optimal temperature of 40°. The Mr of the β-mannanase was estimated to be 33 000 by gel filtration, the Km and Vmax values were 6.17 × 10−3 M and 16.1 × 10−3 nkat, respectively. The activity of the β-mannanase was determined by measuring the reduction of the viscosity and the enhancement of reductive equivalents in β-1,4-GM solutions. The GM-hydrolysis proceeded by a random mechanism. The β-1,4-GM degradation products were identified as Man, Glc, a number of β-1,4-manno- and glucomanno-oligosaccharides and a remarkable amount of a small Mr (3000) GM fraction with an identical Man to Glc ratio as in the genuine GM.
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