First crystal structure of an NADP+-dependent l-arginine dehydrogenase belonging to the μ-crystallin family

Crystal structures of Pseudomonas veronii L-arginine dehydrogenase (L-ArgDH), belonging to the μ-crystallin/ornithine cyclodeaminase family, were determined for the enzyme in complex with L-lysine and NADP+ and with L-arginine and NADPH. The main chain coordinates of the P. veronii L-ArgDH monomer showed notable similarity to those of Archaeoglobus fulgidus L-AlaDH, belonging to the same family, and pro-R specificity similar to L-AlaDH for hydride transfer to NADP+ was postulated. However, the residues recognizing the α-amino group of the substrates differed between the two enzymes. Based on a substrate modeling study, it was proposed that in A. fulgidus L-AlaDH, the amino group of L-alanine interacts via a water molecule (W510) with the side chains of Lys41 and Arg52. By contrast, the α-amino group of L-arginine formed hydrogen bonds with the side chains of Thr224 and Asn225 in P. veronii L-ArgDH. Moreover, the guanidino group of L-arginine was fixed into the active site via hydrogen bonds with the side chain of Asp54. Site-directed mutagenesis suggested that Asp54 plays an important role in maintaining high reactivity against the substrate and that Tyr58 and Lys71 play critical roles in enzyme catalysis.

© 2023. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/