Fig. 5: Cartoon model of the proposed catalytic process of AAR in the two-step pathway.

The NTD, mid-domain, and CTD of AAR are colored blue, yellow, and magenta, respectively. ADO is colored gray. Note that ADO may associate with AAR at several different states (such as S1, S2, and S3), since its binding is for assisting the aldehyde transferring, but not essential for substrate/NADPH binding.