Bioinformatic and biochemical analysis of a novel maltose-forming α-amylase of the GH57 family in the hyperthermophilic archaeon Thermococcus sp. CL1

•We found two maltose-forming α-amylase subgroups in Thermococcus genera.•CL1_0868 (TCMA) is the first maltose-forming α-amylase characterized from Thermococcus species.•TCMA displays dual hydrolysis activity toward α-1,4- and α-1,6-glycosidic linkages and only recognizes maltose.•TCMA displays different optimum conditions depending on the glycosidic linkage of the substrate. Maltose-forming α-amylase is a glycoside hydrolase family 57 (GH57) member that is unique because it displays dual hydrolysis activity toward α-1,4- and α-1,6-glycosidic linkages and only recognizes maltose. This enzyme was previously identified only in Pyrococcus sp. ST04 (PSMA); however, we recently found two homologs subgroups in Thermococcus species. One subgroup (subgroup A) showed relatively high amino acid sequence similarity to PSMA (>71%), while the other subgroup (subgroup B) showed lower homology with PSMA (