Ketosteroid Isomerase
From Proteopedia
Contents |
Ketosteroid Isomerase
Introduction
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Ketosteroid isomerase (KSI, EC#5.3.3.1) is an enzyme that catalyzes the isomerization of 3-oxo-Δ5 ketosteroids to their hormonally active Δ4-conjugated isomers.[1]
This reaction is essential in the biosynthesis of steroids in mammals where KSI is a membrane-bound complex.[2] In bacteria, however, KSI exists as a soluble protein is involves in catabolism of steroids.[2] It is one of the most proficient known enzymes with an essentially diffusion limited rate of catalysis. An NMR solution phase structure of KSI was solved in 1997 by Wu et al.[3]
Structure
Ketosteroid isomerase exits as a 28 kDa homodimeric protein, in which the two dimers related to each other via hydrophobic and electrostatic interactions.[3]
The catalytic site of KSI is extremely hydrophobic.
Enzyme Mechanism
Related Proteins
Available Structures
References
- ↑ Pollack RM. Enzymatic mechanisms for catalysis of enolization: ketosteroid isomerase. Bioorg Chem. 2004 Oct;32(5):341-53. PMID:15381400 doi:10.1016/j.bioorg.2004.06.005
- ↑ 2.0 2.1 Ha NC, Choi G, Choi KY, Oh BH. Structure and enzymology of Delta5-3-ketosteroid isomerase. Curr Opin Struct Biol. 2001 Dec;11(6):674-8. PMID:11751047
- ↑ 3.0 3.1 Wu ZR, Ebrahimian S, Zawrotny ME, Thornburg LD, Perez-Alvarado GC, Brothers P, Pollack RM, Summers MF. Solution structure of 3-oxo-delta5-steroid isomerase. Science. 1997 Apr 18;276(5311):415-8. PMID:9103200
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