Table 2. Comparison of substrate-binding residues between chitinases with the CID and without the CID.
| PDB Code | Subsites for sugar residues | Protein residue | |||
| Residues on the TIM barrel | Conserved residues on the CID | ||||
| Hydrogen bonding | Hydrophobic interaction | Hydrogen bonding | Hydrophobic interaction | ||
| 1EOM (A) | 632 | D126, E128, Q211, Y213, Y272 | F39 | ||
| 633 | D18, R20, E245, Y272 | ||||
| 634 | K42, N85, D87, H129 | F39 | |||
| 641 | R20, E245 | ||||
| 635, 636, 642, 643 | |||||
| 1FFR (B) | +2 | K369, D391 | W275, F396, Y418 | ||
| +1 | E315, D391 | W275, F316, M388 | R446 | ||
| −1 | D313, E315, D391 | Y163, W275, A362, M388, W539 | Y444, R446 | ||
| −2 | E540 | W275, W539 | E473 | I476 | |
| −3 | T276 | W167 | E473 | ||
| −4 | R172 | ||||
| −5 | Y170 | ||||
(A) Interactions between select residues on E. meningoseptica NAGase (1EOM) and bound polysaccharide. (B) Interactions between some residues on S. marcescens chiA (1FFR) and bound substrate (NAG)7. The data are adapted from Waddling et al. [48] and Papanikolau et al. [34]. Conserved residues on the CID from our conservation analysis are in bold.