Structural analysis of plant aminoaldehyde dehydrogenases
Martina Tylichová1, David Kopečný1, Pierre Briozzo2, Solange Moréra3, Jacques Snégaroff2 and Marek Šebela1
1Department of Biochemistry, Faculty of Science, Palacký University, Šlechtitelů 11, CZ-78371 Olomouc, Czech Republic.
2UMR206 Laboratoire de Chimie Biologique, INRA-AgroParisTech, F-78850 Thiverval-Grignon, France.
d'Enzymologie et de Biochimie Structurales, CNRS, F-91198 Gif-sur-Yvette Cedex,
Aminoaldehyde dehydrogenases (AMADH, EC 18.104.22.168) catalyze the terminal step in polyamine catabolism by oxidizing omega-aminoaldehydes like 4-aminobutyraldehyde (ABAL) and 3-aminopropionaldehyde (APAL). Based on their amino acid sequences, the enzymes belong to the same group as betaine aldehyde dehydrogenases (BADHs, EC 22.214.171.124). Presence of two isoenzymes is common in plants. To understand their function, we expressed two AMADHs of 503 amino acids from pea (Pisum sativum, PsAMADH1 and 2) and performed X-ray crystallographic study together with kinetic analysis using a large set of natural and synthetic aminoaldehydes. The structures of bot PsAMADHs in complex with NAD+ coenzyme were refined at 2.4 Å and 2.15 Å resolution. They show that both plant enzymes are dimeric and provide a detailed description of the coenzyme and substrate binding site. Likewise, we analyzed kinetic properties of two AMADHs from tomato (Lycopersicon esculentum, LeAMADH1 and 2) and two isoenzymes from maize (Zea mays, ZmAMADH1 and 2). Except for LeAMADH1, five remaining AMADHs carry C-terminal peroxisomal targeting sequence signal type 1 [S/A]KL and exhibit similar kinetic properties. Although these enzymes are often assigned to BADHs in different databases, our results show that this is no longer correct as all six studied enzymes preferred APAL and ABAL to betaine aldehyde as a substrate. Although substrate specificity can vary among species, in terms of wider substrate specificity the above-mentioned enzymes should be considered as AMADHs and not BADHs.
Supported by grant 522/08/0555 from the Czech Science Foundation and grant MSM 6198959215 from the Ministry of Education, Youth and Sports of the Czech Republic.