Structural highlights
3uzz is a 2 chain structure with sequence from Homo sapiens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
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| Ligands: | , , , |
| Related: | 3uzw, 3uzx, 3uzy |
| Gene: | AKR1D1, SRD5B1 (Homo sapiens) |
| Activity: | Delta(4)-3-oxosteroid 5-beta-reductase, with EC number 1.3.1.3 |
| Resources: | FirstGlance, OCA, RCSB, PDBsum |
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.
Publication Abstract from PubMed
Human aldo-keto reductase 1D1 (AKR1D1) and AKR1C enzymes are essential for bile acid biosynthesis and steroid hormone metabolism. AKR1D1 catalyzes the 5beta-reduction of Delta(4)-3-ketosteroids, whereas AKR1C enzymes are hydroxysteroid dehydrogenases (HSDs). These enzymes share high sequence identity and catalyze 4-pro-(R)-hydride transfer from NADPH to an electrophilic carbon but differ in that one residue in the conserved AKR catalytic tetrad, His(120) (AKR1D1 numbering), is substituted by a glutamate in AKR1D1. We find that the AKR1D1 E120H mutant abolishes 5beta-reductase activity and introduces HSD activity. However, the E120H mutant unexpectedly favors dihydrosteroids with the 5alpha-configuration and, unlike most of the AKR1C enzymes, shows a dominant stereochemical preference to act as a 3beta-HSD as opposed to a 3alpha-HSD. The catalytic efficiency achieved for 3beta-HSD activity is higher than that observed for any AKR to date. High resolution crystal structures of the E120H mutant in complex with epiandrosterone, 5beta-dihydrotestosterone, and Delta(4)-androstene-3,17-dione elucidated the structural basis for this functional change. The glutamate-histidine substitution prevents a 3-ketosteroid from penetrating the active site so that hydride transfer is directed toward the C3 carbonyl group rather than the Delta(4)-double bond and confers 3beta-HSD activity on the 5beta-reductase. Structures indicate that stereospecificity of HSD activity is achieved because the steroid flips over to present its alpha-face to the A-face of NADPH. This is in contrast to the AKR1C enzymes, which can invert stereochemistry when the steroid swings across the binding pocket. These studies show how a single point mutation in AKR1D1 can introduce HSD activity with unexpected configurational and stereochemical preference.
Conversion of human steroid 5beta-reductase (AKR1D1) into 3beta-hydroxysteroid dehydrogenase by single point mutation E120H: example of perfect enzyme engineering.,Chen M, Drury JE, Christianson DW, Penning TM J Biol Chem. 2012 May 11;287(20):16609-22. Epub 2012 Mar 20. PMID:22437839[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
- ↑ Chen M, Drury JE, Christianson DW, Penning TM. Conversion of human steroid 5beta-reductase (AKR1D1) into 3beta-hydroxysteroid dehydrogenase by single point mutation E120H: example of perfect enzyme engineering. J Biol Chem. 2012 May 11;287(20):16609-22. Epub 2012 Mar 20. PMID:22437839 doi:10.1074/jbc.M111.338780
