Desulfurococcus amylolyticus is an anaerobic and hyperthermophilic crenarchaeon that can use various carbohydrates as energy sources. We found a gene encoding a glycoside hydrolase family 57 amylolytic enzymes (DApu) in a putative carbohydrate utilization gene cluster in the genome of D. amylolyticus. This gene has an open reading frame of 1,878 bp and consists of 626 amino acids with a molecular mass of 71 kDa. Recombinant DApu (rDApu) completely hydrolyzed pullulan to maltotriose by attacking α-1,6-glycosidic linkages, and was able to produce glucose and maltose from soluble starch and amylopectin. Although rDApu showed no activity toward α-cyclodextrin (CD) and β-CD, maltooctaose (G8) was detected from reaction with γ-CD. The highest activity of rDApu was measured at pH 5.0 and 95 °C. The half-life of rDApu was 12.7 h at 95 °C and 27 min at 98 °C. Interestingly, rDApu was able to transfer a maltose unit to 6-O-α-maltosyl-β-CD via transglycosylation. Structure analysis using MALDI-TOF/TOF MS and nuclear magnetic resonance revealed that the new transglycosylated products were 61, 64-di-O-maltosyl-β-CD and 61, 63, 65-tri-O-maltosyl-β-CD.
Keywords: Amylopullulanase; Branched cyclodextrin (CD); Desulfurococcus amylolyticus; Pullulan; Transglycosylation.
Copyright © 2018 Elsevier Inc. All rights reserved.