Inhibition of Dog and Human Gastric Lipases by Enantiomeric Phosphonate Inhibitors: A Structure-Activity Study

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• 作者：Nabil Miled ; Alain Roussel ; Cé ; cile Bussetta ; Liliane Berti-Dupuis ; Mireille Riviè ; re ; Gé ; rard Buono ; Robert Verger ; Christian Cambillau ; and Sté ; phane Canaan
• 刊名：Biochemistry
• 出版年：2003
• 出版时间：October 14, 2003
• 年：2003
• 卷：42
• 期：40
• 页码：11587 - 11593
• 全文大小：445K
• 年卷期：v.42,no.40(October 14, 2003)
• ISSN：1520-4995

文摘

The crystal structures of gastric lipases in the apo form [Roussel, A., et al. (1999) J. Biol.Chem. 274, 16995-17002] or in complex with the (R_P)-undecyl butyl phosphonate [C₁₁Y₄(+)] [Roussel,A., et al. (2002) J. Biol. Chem. 277, 2266-2274] have improved our understanding of the structure-activity relationships of acid lipases. In this report, we have performed a kinetic study with dog andhuman gastric lipases (DGL and HGL, respectively) using several phosphonate inhibitors by varying theabsolute configuration of the phosphorus atom and the chain length of the alkyl/alkoxy substitutents.Using the two previously determined structures and that of a new crystal structure obtained with the other(S_P)-phosphonate enantiomer [C₁₁Y₄(-)], we constructed models of phosphonate inhibitors fitting intothe active site crevices of DGL and HGL. All inhibitors with a chain length of fewer than 12 carbonatoms were found to be completely buried in the catalytic crevice, whereas longer alkyl/alkoxy chainswere found to point out of the cavity. The main stereospecific determinant explaining the stronger inhibitionof the S_P enantiomers is the presence of a hydrogen bond involving the catalytic histidine as found in theDGL-C₁₁Y₄(-) complex. On the basis of these results, we have built a model of the first tetrahedralintermediate corresponding to the tristearoyl-lipase complex. The triglyceride molecule completely fillsthe active site crevice of DGL, in contrast with what is observed with other lipases such as pancreaticlipases which have a shallower and narrower active site. For substrate hydrolysis, the supply of watermolecules to the active site might be achieved through a lateral channel identified in the protein core.