A detailed in silico analysis of the amylolytic family GH126 and its possible relatedness to family GH76

The glycoside hydrolase (GH) family 126 was established based on the X-ray structure determination of the amylolytic enzyme CPF_2247 from Clostridium perfringens genome. Its original identification as a putative car-bohydrate-active enzyme was based on its low, yet significant sequence identity to members of the family GH8, which are inverting endo-beta-1,4-glucanases. As the family GH8 forms the clan GH-M with GH48, the CPF_2247 protein also exhibits similarities with members of the family GH48. The original screening of the CPF_2247 on carbohydrate substrates demonstrated its activity on glycogen and amylose, thus classifying this protein as an "alpha-amylase". It should be pointed out, however, there are apparent inconsistencies concerning the exact enzyme specificity of the "amylase" CPF_2247, since it exhibits both the endo-and exo-fashion of action. The family GH126 currently counts similar to 1000 amino acid sequences solely from Bacteria; all belonging to the phylum Firmicutes. The present study delivers the first detailed bioinformatics study of 117 selected amino acid se-quences from the family GH126, featuring the insightful sequence-structure comparison with the aim to define seven conserved sequence regions and elucidate the evolutionary relationships within the family. In addition, a comparative structural analysis of the GH126 members with representatives of other GH families adopting the same (alpha/alpha)(6)-barrel catalytic domain fold indicates the possible sharing a catalytic residue between the families GH126 and GH76.