1ea2

<table><tr><td colspan='2'>[[1ea2]] is a 1 chain structure. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1EA2 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1EA2 FirstGlance]. <br>

</td></tr><tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat"><div style='overflow: auto; max-height: 3em;'>[[1c7h|1c7h]], [[1dmm|1dmm]], [[1dmn|1dmn]], [[1dmq|1dmq]], [[1e3n|1e3n]], [[1e3r|1e3r]], [[1e3v|1e3v]], [[1e97|1e97]], [[1opy|1opy]], [[4tsu|4tsu]]</div></td></tr>

<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[https://en.wikipedia.org/wiki/Steroid_Delta-isomerase Steroid Delta-isomerase], with EC number [https://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.3.3.1 5.3.3.1] </span></td></tr>

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== Publication Abstract from PubMed ==

Delta5-3-ketosteroid isomerase (KSI) from Pseudomonas putida Biotype B catalyzes the allylic isomerization of Delta5-3-ketosteroids to their conjugated Delta4-isomers via a dienolate intermediate. Two electrophilic catalysts, Tyr-14 and Asp-99, are involved in a hydrogen bond network that comprises Asp-99 Odelta2...O of Wat504...Tyr-14 Oeta...Tyr-55 Oeta.Tyr-30 Oeta in the active site of P. putida KSI. Even though neither Tyr-30 nor Tyr-55 plays an essential role in catalysis by the KSI, the catalytic activity of Y14F could be increased ca. 26-51-fold by the additional Y30F and/or Y55F mutation in the hydrogen bond network. To identify the structural basis for the pseudoreversion in the KSI, crystal structures of Y14F and Y14F/Y30F/Y55F have been determined at 1.8 and 2.0 A resolution, respectively. Comparisons of the two structures near the catalytic center indicate that the hydrogen bond between Asp-99 Odelta2 and C3-O of the steroid, which is perturbed by the Y14F mutation, can be partially restored to that in the wild-type enzyme by the additional Y30F/Y55F mutations. The kinetic parameters of the tyrosine mutants with the additional D99N or D99L mutation also support the idea that Asp-99 contributes to catalysis more efficiently in Y14F/Y30F/Y55F than in Y14F. In contrast to the catalytic mechanism of Y14F, the C4 proton of the steroid substrate was found to be transferred to the C6 position in Y14F/Y30F/Y55F with little exchange of the substrate 4beta-proton with a solvent deuterium based on the reaction rate in D2O. Taken together, our findings strongly suggest that the improvement in the catalytic activity of Y14F by the additional Y30F/Y55F mutations is due to the changes in the structural integrity at the catalytic site and the resulting restoration of the proton-transfer mechanism in Y14F/Y30F/Y55F.

Pseudoreversion of the catalytic activity of Y14F by the additional substitution(s) of tyrosine with phenylalanine in the hydrogen bond network of delta 5-3-ketosteroid isomerase from Pseudomonas putida biotype B.,Choi G, Ha NC, Kim MS, Hong BH, Oh BH, Choi KY Biochemistry. 2001 Jun 12;40(23):6828-35. PMID:11389596<ref>PMID:11389596</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

<references/>

[[Category: Steroid Delta-isomerase]]

[[Category: Choi, G]]

[[Category: Choi, K Y]]

[[Category: Ha, N C]]

[[Category: Hong, B H]]

[[Category: Kim, M S]]

[[Category: Ketosteroid isomerase]]