MAIZE ALDEHYDE DEHYDROGENASES FROM THE FAMILY 7 AND 10

Radka Končitíková¹, Martina Tylichová¹, David Kopečný^1,2, Solange Moréra², Armelle Vigouroux², Jan Frömmel¹, Marek Šebela^1,2

¹Department of Protein Biochemistry and Proteomics, Centre of the Region Haná for Biotechnological and Agricultural Research and
²Department of Biochemistry, Faculty of Science, Palacký University, Šlechtitelů 11, CZ-783 71 Olomouc, Czech Republic; ²Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, F-91198 Gif-sur-Yvette Cedex, France

Aldehyde dehydrogenases (ALDHs) comprise a protein superfamily of NAD(P)⁺-dependent enzymes (EC 1.2.1). They have been considered as general detoxifying enzymes, which eliminate biogenic and xenobiotic aldehydes to the corresponding carboxylic acids. Up to date, twelve ALDH families have been described in plants, but only a small number of the enzymes have been functionally characterized despite the existence of a large number of coding genes. In this work, we analyzed several ALDHs from maize (Zea mays) belonging to the families 2, 3, 7 and 10 with a special interest in the latter two families. For ALDH7, there are also synonymous terms Δ¹-piperideine-6-carboxylate dehydrogenase or α-aminoadipic semialdehyde dehydrogenase used. ALDH7 is mainly connected with lysine metabolism as it catalyzes the conversion of α-aminoadipic semialdehyde (α-AASA) to α-aminoadipate. ALDH10 is an aminoaldehyde dehydrogenase (AMADH, EC.1.2.1.19), often reported as a betaine aldehyde dehydrogenase (BADH, E.C. 1.2.1.8), and oxidizes ω-aminoaldehydes to the corresponding amino acids such as β-alanine, γ-aminobutyric acid, g-butyrobetaine or glycine betaine. The enzyme is connected with the metabolic pathways of polyamines, arginine, lysine and choline. Selected genes coding for ALDHs were cloned and expressed in T7 E. coli cells. The recombinant enzymes were thoroughly characterized and their identity was verified by MALDI-TOF peptide mass fingerprinting. Maize ALDH7 utilizes NAD⁺ but not NADP⁺ as a coenzyme and prefers α-AASA to other aliphatic and aromatic aldehydes. Three maize ALDH10 members (AMADH1a, 1b and 2) preferentially oxidize 3-aminopropionaldehyde, 4-aminobutyraldehyde and 4-guanidinobutyraldehyde (but not α-AASA) and they use NAD⁺ as a coenzyme. Our results confirm a previous suggestion that the presence of two highly unconserved Trp residues at the substrate channel results in higher affinity to ω-aminoaldehydes. Representatives of both families were crystallized. So far, the crystal structure of ZmAMADH1 has been solved up to 1.95 Ǻ resolution.

This work was supported by grant P501/11/1591 and 522/08/0555 from the Czech Science Foundation and by grant PrF_2011_031 from the Faculty of Science, Palacký University in Olomouc.