Model of TfHex. A. Side view of monomeric TfHex with active site amino acids shown in magenta and stick representation. B. Dimeric TfHex. Each monomer is colored by a different color, active site amino acids are shown in magenta. C. Overlay of the active site of hexosaminidases from S. plicatus (green), T. flavus (red), human (blue) and O. furnacalis (magenta), the standard substrate is colored in yellow, hydrogen bonds are shown by yellow dotted lines. D. Overlay of bacterial S. plicatus (green), human (blue), insect O. furnacalis (red) hexosaminidases and TfHex (magenta). Loops 1 (left) and 2 (right) are shown in cartoon representation. Active site amino acids of TfHex are shown in stick representation and labeled with one letter code. Glu 332 and Trp 509 belong to loop 1 and 2 correspondingly.