A NEW MALTODEXTRIN PHOSPHORYLASE FROM CORYNEBACTERIUM-CALLUNAE FOR THE PRODUCTION OF GLUCOSE-1-PHOSPHATE

During a screening for new microbial alpha-glucan phosphorylases coryn ebacteria were found to be promising, not-yet-identified producers of these particular enzymes. A maltodextrin phosphorylase (MDP) from Cory nebacterium callunae was isolated, partially characterized, and used f or the production of glucose-1-phosphate (G-1-P) from different a-gluc ans. In fermentor cultivations of C. callunae using maltodextrin as th e inducing carbohydrate component, an MDP activity of approximately 8- 10 units/g biomass (equivalent to 250 units/l) could be obtained. Cont aminating activities of phosphoglucomutase and phosphatase were remove d by ammonium sulphate precipitation followed by hydrophobic interacti on chromatography on phenyl-sepharose. The partially (14-fold) purifie d MDP showed pH optima of 6.8 and 6.0 in the direction of phosphorolys is and synthesis, respectively. In the presence of 50 mM inorganic pho sphate the enzyme was stable for more than 2 months at room temperatur e. The new MDP is capable of producing G-1-P from maltodextrins, solub le starch, and glycogen with decreasing order of activity. The same gl ucans were accepted as primers in the direction of synthesis. Increasi ng pH values favoured the formation of G-1-P and optimized conditions for its production were established at a pH of 7.5. The maximum attain able yields of G-1-P by the action of MDP are limited by mainly two fa ctors: (1) no more than approximately 20% of the initial inorganic pho sphate could be converted into G-1-P and (2) the highest degrees of ph osphorolytic maltodextrin degradation were in the range 30-35%. These values could be increased to more than 60% after pretreatment of the m altodextrins with pullulanase.