8cho

CRYSTAL STRUCTURE OF DELTA5-3-KETOSTEROID ISOMERASE FROM PSEUDOMONAS TESTOSTERONI

spinqualitylabelsall models 8cho, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 8cho is a 1 chain structure with sequence from Comamonas testosteroni. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: P4C Activity: Steroid Delta-isomerase, with EC number 5.3.3.1 Resources: FirstGlance, OCA, RCSB, PDBsum 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 Bacterial Delta 5-3-ketosteroid isomerase (KSI) from Pseudomonas testosteroni has been intensively studied as a prototype for understanding an enzyme-catalyzed allylic rearrangement involving intramolecular proton transfer. Asp38 serves as a general base to abstract the proton from the steroid C4-H, which is a much stronger base than the carboxyl group of this residue. This unfavorable proton transfer requires 11 kcal/mol of energy which has to be provided by favorable interactions between catalytic residues and substrate in the course of the catalytic reaction. How this energy is provided at the active site of KSI has been a controversial issue, and inevitably the enzyme mechanism is not settled. To resolve these issues, we have determined the crystal structure of this enzyme at 2.3 A resolution. The crystal structure revealed that the active site environment of P. testosteroni KSI is nearly identical to that of Pseudomonas putida KSI, whose structure in complex with a reaction intermediate analogue we have determined recently. Comparison of the two structures clearly indicates that the two KSIs should share the same enzyme mechanism involving the stabilization of the dienolate intermediate by the two direct hydrogen bonds to the dienolate oxyanion, one from Tyr14 OH and the other from Asp99 COOH. Mutational analysis of the two residues and other biochemical data strongly suggest that the hydrogen bond of Tyr14 provides the more significant contribution than that of Asp99 to the requisite 11 kcal/mol of energy for the catalytic power of KSI. Crystal structure and enzyme mechanism of Delta 5-3-ketosteroid isomerase from Pseudomonas testosteroni.,Cho HS, Choi G, Choi KY, Oh BH Biochemistry. 1998 Jun 9;37(23):8325-30. PMID:9622484 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Ketosteroid Isomerase

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