Two D-2-hydroxy-acid dehydrogenases in Arabidopsis thaliana with catalytic capacities to participate in the last reactions of the methylglyoxal and beta-oxidation pathways.
The Arabidopsis thaliana locus At5g06580 encodes an ortholog to Saccharomyces cerevisiae d-lactate dehydrogenase (AtD-LDH). The recombinant protein is a homodimer of 59-kDa subunits with one FAD per monomer. A substrate screen indicated that AtD-LDH catalyzes the oxidation of d- and l-lactate, d-2-hydroxybutyrate, glycerate, and glycolate using cytochrome c as an electron acceptor. AtD-LDH shows a clear preference for d-lactate, with a catalytic efficiency 200- and 2000-fold higher than that for l-lactate and glycolate, respectively, and a K(m) value for d-lactate of approximately 160 microm. Knock-out mutants showed impaired growth in the presence of d-lactate or methylglyoxal. Collectively, the data indicated that the protein is a d-LDH that participates in planta in the methylglyoxal pathway. Web-based bioinformatic tools revealed the existence of a paralogous protein encoded by locus At4g36400. The recombinant protein is a homodimer of 61-kDa subunits with one FAD per monomer. A substrate screening revealed highly specific d-2-hydroxyglutarate (d-2HG) conversion in the presence of an organic cofactor with a K(m) value of approximately 580 microm. Thus, the enzyme was characterized as a d-2HG dehydrogenase (AtD-2HGDH). Analysis of knock-out mutants demonstrated that AtD-2HGDH is responsible for the total d-2HGDH activity present in A. thaliana. Gene coexpression analysis indicated that AtD-2HGDH is in the same network as several genes involved in beta-oxidation and degradation of branched-chain amino acids and chlorophyll. It is proposed that AtD-2HGDH participates in the catabolism of d-2HG most probably during the mobilization of alternative substrates from proteolysis and/or lipid degradation.
Engqvist
Martin
M
Botanisches Institut, Universität zu Köln, Gyrhofstrasse 15, 50931 Cologne, Germany.
Drincovich
María F
MF
Flügge
Ulf-Ingo
UI
Maurino
Verónica G
VG
D017360:Arabidopsis / Q000378:metabolism*; D002384:Catalysis; D002734:Chlorophyll / Q000737:chemistry; D019295:Computational Biology / Q000379:methods; D045304:Cytochromes c / Q000737:chemistry; D019281:Dimerization; D007700:Kinetics; D045022:Lactate Dehydrogenases / Q000737:chemistry* / Q000378:metabolism; D008055:Lipids / Q000737:chemistry; D009154:Mutation; D010100:Oxygen / Q000737:chemistry*; D010802:Phylogeny; D011765:Pyruvaldehyde / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry; D013379:Substrate Specificity
D008055:Lipids; D011994:Recombinant Proteins; D002734:Chlorophyll; D011765:Pyruvaldehyde; D045304:Cytochromes c; D045022:Lactate Dehydrogenases; C071195:D-lactate dehydrogenase; D010100:Oxygen