title: Substrate-induced conformational change and isomerase activity of dienelactone hydrolase and its site-specific mutants.
abstract: Studies of the interactions of dienelactone hydrolase (DLH) and its mutants with both E and Z dienelactone substrates show that the enzyme exhibits two different conformational responses specific for hydrolysis of each of its substrate isomers. DLH facilitates hydrolysis of the Z dienelactone through an unusual charge-relay system that is initiated by interaction between the substrate carboxylate and an enzyme arginine residue that activates an otherwise non-nucleophilic cysteine. The E dienelactone does not display this substrate-arginine binding interaction, but instead induces an alternate conformational response that promotes hydrolysis. Furthermore, the substitution of cysteine 123 for serine (C123S) in DLH, instead of inactivating the enzyme as is typical for this active-site mutation, changes the catalysis from substrate hydrolysis to isomerisation. This is due to the deacylation of the acyl-enzyme intermediates being much slower, thereby increasing their lifetimes and allowing for their interconversion through isomerisation, followed by relactonisation.
authors: Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia.
authors: Ian
authors: I
authors: Walker
authors: James E
authors: JE
authors: Hennessy
authors: David L
authors: DL
authors: Ollis
authors: Christopher J
authors: CJ
authors: Easton
mesh_terms: D055162:Biocatalysis; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020134:Catalytic Domain; D006868:Hydrolysis; D007783:Lactones / Q000737:chemistry / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011487:Protein Conformation; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D007783:Lactones; C084081:dienelactone; D002265:Carboxylic Ester Hydrolases; C046130:carboxymethylenebutenolidase