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Fig. 5 | Biotechnology for Biofuels

Fig. 5

From: The Coptotermes gestroi aldo–keto reductase: a multipurpose enzyme for biorefinery applications

Fig. 5

Sequence comparison and structural assignment. a Multiple sequence alignment of CgAKR with members of the most similar related families AKR1–5. Despite the low identity among CgAKR-1 and other AKR enzymes, the catalytic residues (red) and the residues that interacted with the cofactor (blue) had a high degree of similarity. The residues that surrounded the substrate (yellow) were more diverse between each family, reflecting the specificity for different substrates. The position that interacted with both the substrate and cofactor is shown in green. One of the main differences between CgAKR-1 and the other enzymes was the presence of a longer loop, known as loop B (magenta), located in the substrate-binding site. b Positioning of the important amino acids in the CgAKR-1 crystallographic structure (the colors in b are the same as those in a). c Substrate-binding site. The cavity in the CgAKR-1 structure, represented here as a blue surface, was determined to be the substrate-binding site by comparison with other substrate-complexed AKRs. Therefore, the pocket was mainly delimited by the cofactor (NADP) and nine amino acids with different properties, including R229 from loop B (observed only in CgAKR-1). d Superposition of CgAKR-1 with other AKRs from different families: 1A1 complexed with 3,5-dichlorosalicylic acid (gray arrow) in gray (PDBid 3cv7), 1B in blue (PDBid 4hbk), 1C in green (PDBid 1ihi), 1D in red (PDBid 3buv), 2B in orange (PDBid 1mi3), 4A in yellow (PDBid 1zgd), and 5C in black (PDBid 1hw6). The loops comprised the entrance to the substrate-binding site. Despite the discernible variations in size and position, CgAKR-1 (magenta) had one loop (loop B, indicated with a magenta arrow) that was longer than the others. This loop also contained an arginine (R229) that may interact with the substrate

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