Amylolytic enzymes from the yeast Lipomyces kononenkoae

The Lipomyces kononenkoae α-amylases LKA1 and LKA2 belong to the glycoside hydrolase family 13 and exhibit specificity towards α-1,4 and α-1,6 linkages in starch and related substrates. LKA1 exhibits specificity towards α-1,4 and α-1,6 linkages and large amounts of reducing sugars are liberated from highly branched amylopectin and glycogen and linear amylose. LKA2, on the other hand, shows high reactivity towards lintner starch, dextrin and amylase, although only small amounts of reducing sugars are liberated from branched substrates, such as amylopectin and glycogen. These enzymes share the four conserved segments of the catalytic domain found in other members of the family, but have some major variant amino acids within these segments. In addition, LKA1 consists of an N-terminal starch-binding domain (SBD). This is the only α-amylase known to possess this N-terminal domain and it exhibits homology to the N-terminal SBD of Rhizopus oryzae glucoamylase. It shares no homology with the C-terminal starch-binding domains present in the cyclodextrin glucanotransferases, glucoamylases or α-amylases. The evolutionary tree based on the sequence alignment of SBDs reveals that the N-terminal SBDs are separated from the C-terminal SBDs.