3Beta-brassinosteroid dehydrogenase activity in Arabidopsis and tomato.
Enzymatic conversion of 24-epiteasterone to 3-dehydro-24-epiteasterone, representing a reversible step in the biosynthesis of 24R-methyl brassinosteroids, was monitored in vitro in Arabidopsis thaliana and Lycopersicon esculentum using fluorescent tagging and HPLC analysis. In both species 24-epiteasterone was metabolized by the cytosolic fraction of induced root-callus suspension cultures in a NAD dependent manner. This 3beta-dehydrogenation was only slightly inhibited by 12-fold excess of other 3beta-hydroxy intermediates of the early (cathasterone) and late C-6 oxidation pathway (6-deoxo-cathasterone, 6-deoxo-teasterone), indicating a rather specific protein. 3-Dehydro-6-deoxoteasterone and 3alpha-hydroxy intermediates of brassinosteroid biosynthesis did not reduce conversion of 24-epiteasterone to 3-dehydro-24-epiteasterone. In contrast to light-grown cultures the reaction was clearly inhibited in the dark.
Stündl
U
U
Max-Planck-Institut für Chemische Okologie, Carl-Zeiss-Promenade 10, D-07745 Jena, Germany.
Schneider
B
B
D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid; D003624:Darkness; D008027:Light; D018551:Solanum lycopersicum / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D013256:Steroids / Q000378:metabolism; D013379:Substrate Specificity
D013256:Steroids; D009243:NAD; D000429:Alcohol Oxidoreductases; C448642:3beta-brassinosteroid dehydrogenase