Synthesis of β‐glucans in Prototheca zopfii

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Abstract
Membrane preparations from the non-photosynthetic alga Prototheca zopfii incorporate glucose from UDP-[3H]glucose into the trichloroacetic-acid-insoluble fraction and the polysaccharides insoluble in hot alkali. Time course and pulse-chase experiments indicate that the acid-insoluble fraction was a precursor of the alkali-insoluble fraction. Isolation of 3H-labeled membrane or soluble fraction showed that only membrane fractions were able to transfer radioactivity into polysaccharides. Treatment of glucosylated membranes with trypsin or cellulase only partially affect their transfer ability, indicating that the precursor was internalized in vesicles. Analysis of the in vitro synthesized polysaccharides by enzymatic and acid hydrolysis showed that glucose and cellobiose were present as radioactive sugars. Permethylation of the polysaccharide indicates that 80% of the glucose was .beta.-1,4-bonded with 20% in .beta.-1,3-linkages. This polysaccharide was found to be identical with the cell-wall .beta.-glucan obtained in vivo [Rivas, L. A. and Pont Lezica, R. (1978) Planta (Berl.) 165, 348-353].

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