ENZYMATIC-SYNTHESIS OF ALPHA-GLUCOSE-1-PHOSPHATE - A STUDY EMPLOYING A NEW ALPHA-1,4 GLUCAN PHOSPHORYLASE FROM CORYNEBACTERIUM-CALLUNAE

In synthetic pathways to complex carbohydrates such as oligosaccharide s or nucleotide sugars the activated sugar l-phosphates serve as impor tant starting molecules. In this study the enzymatic synthesis of alph a-glucose-l-phosphate (Glc-1-P) has been investigated using a new bact erial alpha-glucan phosphorylase from Corynebacterium callunae. The ma jor factors governing the rate of reaction and the attainable degree o f substrate conversion have been identified and, accordingly, for opti mizing the yield and limiting reaction time for the enzymatic process several points must be considered: (i) the pH-dependent equilibrium of reaction, (ii) product inhibition of the phosphorylase and (iii) enzy matic cleavage of alpha-1,6 glycosidic linkages present in alpha-1,4-g lucans such as starch or maltodextrins by pullulanases to improve thei r phosphorolytic conversion. Results obtained in continuous experiment s with the phosphorylase retained in an ultrafiltration membrane react or confirmed the complete operational stability of the enzyme for seve ral days at 30 degrees C. Since no more than approximately 18% of the inorganic phosphate can be converted into Glc-I-P an efficient procedu re for phosphate and product recovery will be particularly important.