Structural highlights
Disease
[AK1D1_HUMAN] Defects in AKR1D1 are the cause of congenital bile acid synthesis defect type 2 (CBAS2) [MIM:235555]; also known as cholestasis with delta(4)-3-oxosteroid 5-beta-reductase deficiency. Patients with this liver disease show absence or low levels of chenodeoxycholic acid and cholic acid in plasma and urine.[1] [2]
Function
[AK1D1_HUMAN] Efficiently catalyzes the reduction of progesterone, androstenedione, 17-alpha-hydroxyprogesterone and testosterone to 5-beta-reduced metabolites. The bile acid intermediates 7-alpha,12-alpha-dihydroxy-4-cholesten-3-one and 7-alpha-hydroxy-4-cholesten-3-one can also act as substrates.
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
AKR1D1 (steroid 5beta-reductase) reduces all Delta(4)-3-ketosteroids to form 5beta-dihydrosteroids, a first step in the clearance of steroid hormones and an essential step in the synthesis of all bile acids. The reduction of the carbon-carbon double bond in an alpha,beta-unsaturated ketone by 5beta-reductase is a unique reaction in steroid enzymology because hydride transfer from NADPH to the beta-face of a Delta(4)-3-ketosteroid yields a cis-A/B-ring configuration with an approximately 90 degrees bend in steroid structure. Here, we report the first x-ray crystal structure of a mammalian steroid hormone carbon-carbon double bond reductase, human Delta(4)-3-ketosteroid 5beta-reductase (AKR1D1), and its complexes with intact substrates. We have determined the structures of AKR1D1 complexes with NADP(+) at 1.79- and 1.35-A resolution (HEPES bound in the active site), NADP(+) and cortisone at 1.90-A resolution, NADP(+) and progesterone at 2.03-A resolution, and NADP(+) and testosterone at 1.62-A resolution. Complexes with cortisone and progesterone reveal productive substrate binding orientations based on the proximity of each steroid carbon-carbon double bond to the re-face of the nicotinamide ring of NADP(+). This orientation would permit 4-pro-(R)-hydride transfer from NADPH. Each steroid carbonyl accepts hydrogen bonds from catalytic residues Tyr(58) and Glu(120). The Y58F and E120A mutants are devoid of activity, supporting a role for this dyad in the catalytic mechanism. Intriguingly, testosterone binds nonproductively, thereby rationalizing the substrate inhibition observed with this particular steroid. The locations of disease-linked mutations thought to be responsible for bile acid deficiency are also revealed.
Crystal structure of human liver Delta4-3-ketosteroid 5beta-reductase (AKR1D1) and implications for substrate binding and catalysis.,Di Costanzo L, Drury JE, Penning TM, Christianson DW J Biol Chem. 2008 Jun 13;283(24):16830-9. Epub 2008 Apr 11. PMID:18407998[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Lemonde HA, Custard EJ, Bouquet J, Duran M, Overmars H, Scambler PJ, Clayton PT. Mutations in SRD5B1 (AKR1D1), the gene encoding delta(4)-3-oxosteroid 5beta-reductase, in hepatitis and liver failure in infancy. Gut. 2003 Oct;52(10):1494-9. PMID:12970144
- ↑ Gonzales E, Cresteil D, Baussan C, Dabadie A, Gerhardt MF, Jacquemin E. SRD5B1 (AKR1D1) gene analysis in delta(4)-3-oxosteroid 5beta-reductase deficiency: evidence for primary genetic defect. J Hepatol. 2004 Apr;40(4):716-8. PMID:15030995 doi:10.1016/j.jhep.2003.12.024
- ↑ Di Costanzo L, Drury JE, Penning TM, Christianson DW. Crystal structure of human liver Delta4-3-ketosteroid 5beta-reductase (AKR1D1) and implications for substrate binding and catalysis. J Biol Chem. 2008 Jun 13;283(24):16830-9. Epub 2008 Apr 11. PMID:18407998 doi:http://dx.doi.org/10.1074/jbc.M801778200
