Active Site and Loop 4 Movements within Human Glycolate Oxidase: Implications for Substrate Specificity and Drug Design
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- 作者：Michael S. Murray ; Ross P. Holmes ; W. Todd Lowther
- 刊名：Biochemistry
- 出版年：2008
- 出版时间：February 26, 2008
- 年：2008
- 卷：47
- 期：8
- 页码：2439 - 2449
- 全文大小：845K
- 年卷期：v.47,no.8(February 26, 2008)
- ISSN：1520-4995
文摘
Human glycolate oxidase (GO) catalyzes the FMN-dependent oxidation of glycolate toglyoxylate and glyoxylate to oxalate, a key metabolite in kidney stone formation. We report herein thestructures of recombinant GO complexed with sulfate, glyoxylate, and an inhibitor, 4-carboxy-5-dodecylsulfanyl-1,2,3-triazole (CDST), determined by X-ray crystallography. In contrast to most 
-hydroxyacid oxidases including spinach glycolate oxidase, a loop region, known as loop 4, is completely visiblewhen the GO active site contains a small ligand. The lack of electron density for this loop in the GO-CDST complex, which mimics a large substrate, suggests that a disordered to ordered transition mayoccur with the binding of substrates. The conformational flexibility of Trp110 appears to be responsiblefor enabling GO to react with -hydroxy acids of various chain lengths. Moreover, the movement ofTrp110 disrupts a hydrogen-bonding network between Trp110, Leu191, Tyr134, and Tyr208. This lossof interactions is the first indication that active site movements are directly linked to changes in theconformation of loop 4. The kinetic parameters for the oxidation of glycolate, glyoxylate, and 2-hydroxyoctanoate indicate that the oxidation of glycolate to glyoxylate is the primary reaction catalyzed by GO,while the oxidation of glyoxylate to oxalate is most likely not relevant under normal conditions. However,drugs that exploit the unique structural features of GO may ultimately prove to be useful for decreasingglycolate and glyoxylate levels in primary hyperoxaluria type 1 patients who have the inability to convertperoxisomal glyoxylate to glycine.
-hydroxyacid oxidases including spinach glycolate oxidase, a loop region, known as loop 4, is completely visiblewhen the GO active site contains a small ligand. The lack of electron density for this loop in the GO-CDST complex, which mimics a large substrate, suggests that a disordered to ordered transition mayoccur with the binding of substrates. The conformational flexibility of Trp110 appears to be responsiblefor enabling GO to react with -hydroxy acids of various chain lengths. Moreover, the movement ofTrp110 disrupts a hydrogen-bonding network between Trp110, Leu191, Tyr134, and Tyr208. This lossof interactions is the first indication that active site movements are directly linked to changes in theconformation of loop 4. The kinetic parameters for the oxidation of glycolate, glyoxylate, and 2-hydroxyoctanoate indicate that the oxidation of glycolate to glyoxylate is the primary reaction catalyzed by GO,while the oxidation of glyoxylate to oxalate is most likely not relevant under normal conditions. However,drugs that exploit the unique structural features of GO may ultimately prove to be useful for decreasingglycolate and glyoxylate levels in primary hyperoxaluria type 1 patients who have the inability to convertperoxisomal glyoxylate to glycine.