First crystal structure of an NADP(+)-dependent L-arginine dehydrogenase belonging to the mu-crystallin family

Crystal structures of Pseudomonas veronii L-arginine dehydrogenase (L-ArgDH), belonging to the mu-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 a-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 alpha-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.

Automated summary

The crystal structures of Pseudomonas veronii L-arginine dehydrogenase in complex with different substrates were studied. The enzyme showed similarities with Archaeoglobus fulgidus L-AlaDH in terms of structure and specificity, but had different residues recognizing the substrates' amino groups.