Proteins, nucleic acids (DNA and RNA), and polysaccharides are three major important biomacromolecules. Cellulose is the most abundant organic substance occurring on the earth. It is a stereoregular polysaccharide having ß(1-4) glycosidic linkage. The chemical syntheses so far attempted failed in all cases, although automatic synthesis equipment of proteins and nucleic acids have become available. Recently, however, we succeeded for the first time in the chemical synthesis of cellulose by a condensation polymerization of p-cellobiosyl fluoride monomer in an organic solvent/buffer system, where cellulase, an extracellular hydrolysis enzyme of cellulose, was used as catalyst. The polymerization was carried out with a crude enzyme in acetonitrile-buffer (5:1) solvent. Then, the product, "synthetic cellulose" showed cellulose II allomorph, the thermodynamically more stable form . This is quite reasonable in terms of the general behaviors of cellulose for heat and alkaline treatments. Cellulose I is a metastable form and has long been believed to be produced only in living transmission electron microscopy, electron diffraction, and cellobiohydrolase 1 (CBH I)-colloidal gold binding. The success is due to the employment of a partially purified cellulase enzyme and to the solvent composition of acetonitrile-buffer (2:1). This reaction system is expected to involve a very specific situation to favor the cellulose I formation. The mechanism of the in vitro formation of cellulose I may provide helpful suggestions for that of the biosynthesis of cellulose.
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