Synthesis of Cellulose by Enzyme Preparations from the Developing Cotton Boll

Abstract

RECENTLY an enzyme system from mung bean seedlings was described which catalyses the incorporation of radio-activity into cellulose from guanosine diphosphate D-glucose labelled with ¹⁴C in the D-glucosyl moiety¹. The extent of this incorporation was considerably stimu lated by the addition of GDP-D-mannose to the reaction mixtuies. This effect was later shown to result from the formation of some as yet uncharacterized polysaccharide, probably a glucomannan². The synthesis of this compound also appeared to proceed at a rate many times that at which cellulose was formed by the same preparations. Sugars other than D-glucose, chiefly D-xylose or D-mannose, have been found associated with the cellulosic fractions of most plant species, but cotton fibres consist almost entirely of β-1,4 linked D-glucosyl residues³. It was therefore of interest to learn whether ¹⁴C-labelled D-glucose from GDP-D-glucose ¹⁴C could be incorporated into the cellulose of cotton fibres in vitro and whether other polysaccharides were formed by the same cell-free enzyme system. The experiments reported here demonstrate that both these processes are brought about by enzymes isolated from the developing cotton boll.