ENZYMES FROM SULFOLOBUS-SHIBATAE FOR THE PRODUCTION OF TREHALOSE AND GLUCOSE FROM STARCH

Enzymes that convert starch and dextrins to alpha,alpha-trehalose and glucose were found in cell homogenates of the hyperthermophilic acidop hilic archaeon Sulfolobus shibatae DMS 5389. Three enzymes were purifi ed and characterized. The first, the S. shibatae trehalosyl dextrin fo rming enzyme (SsTDFE), transformed starch and dextrins to the correspo nding trehalosyl derivatives with an intramolecular transglycosylation process that converted the glucosidic linkage at the reducing end fro m alpha-1,4 to alpha-1,1. The second, the S. shibatae trehalose-formin g enzyme (SsTFE), hydrolyzed the alpha-1,4 linkage adjacent to the alp ha-1,1 bond of trehalosyl dextrins, forming trehalose and lower molecu lar weight dextrins. These two enzymes had molecular masses of 80 kDa and 65 kDa, respectively, and showed the highest activities at pH 4.5. The apparent optimal temperature for activity was 70 degrees C for Ss TDFE and 85 degrees C for SsTFE. The third enzyme identified was an al pha-glycosidase (Ss alpha Gly), which catalyzed the hydrolysis of the alpha-1,4 glucosidic linkages in starch and dextrins, releasing glucos e in a stepwise manner from the nonreducing end of the polysaccharide chain. The enzyme had a molecular mass of 313 kDa and showed the highe st activity at pH 5.5 and at 85 degrees C.