At5g50600 encodes a member of the short-chain dehydrogenase reductase superfamily with 11beta- and 17beta-hydroxysteroid dehydrogenase activities associated with Arabidopsis thaliana seed oil bodies.
In a previous work, we presented evidence for the presence of a protein encoded by At5g50600 in oil bodies (OBs) from Arabidopsis thaliana [P. Jolivet, E. Roux, S. D'Andrea, M. Davanture, L. Negroni, M. Zivy, T. Chardot, Protein composition of oil bodies in Arabidopsis thaliana ecotype WS, Plant Physiol. Biochem. 42 (2004) 501-509]. Using specific antibodies and proteomic techniques, we presently confirm the existence of this protein, which is a member of the short-chain steroid dehydrogenase reductase superfamily. We have measured its activity toward various steroids (cholesterol, dehydroepiandrosterone, cortisol, corticosterone, estradiol, estrone) and NAD(P)(H), either within purified OBs or as a purified bacterially expressed chimera. Both enzymatic systems (OBs purified from A. thaliana seeds as well as the chimeric enzyme) exhibited hydroxysteroid dehydrogenase (HSD) activity toward estradiol (17beta-hydroxysteroid) with NAD+ or NADP+, NADP+ being the preferred cofactor. Low levels of activity were observed with cortisol or corticosterone (11beta-hydroxysteroids), but neither cholesterol nor DHEA (3beta-hydroxysteroids) were substrates, whatever the cofactor used. Similar activity profiles were found for both enzyme sources. Purified OBs were found to be also able to catalyze estrone reduction (17beta-ketosteroid reductase activity) with NADPH. The enzyme occurring in A. thaliana OBs can be classified as a NADP+-dependent 11beta-,17beta-hydroxysteroid dehydrogenase/17beta-ketosteroid reductase. This enzyme probably corresponds to AtHSD1, which is encoded by At5g50600. However, its physiological role and substrates still remain to be determined.
d'Andréa
S
S
Institut National de la Recherche Agronomique, UMR Chimie Biologique, CBAI INRA INA PG, BP1, F-78850 Thiverval Grignon, France.
Canonge
M
M
Beopoulos
A
A
Jolivet
P
P
Hartmann
M A
MA
Miquel
M
M
Lepiniec
L
L
Chardot
T
T
D015067:17-Hydroxysteroid Dehydrogenases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004958:Estradiol / Q000378:metabolism; D064429:Fatty Acid Synthases / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010802:Phylogeny; D010938:Plant Oils / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D013379:Substrate Specificity
D029681:Arabidopsis Proteins; D010938:Plant Oils; D011994:Recombinant Proteins; D004958:Estradiol; D009249:NADP; D015067:17-Hydroxysteroid Dehydrogenases; C044256:3 (or 17)-beta-hydroxysteroid dehydrogenase; C036543:short chain trans-2-enoyl-CoA reductase; D009247:NADH, NADPH Oxidoreductases; D064429:Fatty Acid Synthases