Catalysis by dienelactone hydrolase: A variation on the protease mechanism

Abstract

Dienelactone hydrolase (DLH), an enzyme from the beta-ketoadipate pathway, catalyzes the hydrolysis of dienelactone to maleylacetate. Our inhibitor binding studies suggest that its substrate, dienelactone, is held in the active site by hydrophobic interactions around the lactone ring and by the ion pairs between its carboxylate and Arg-81 and Arg-206. Like the cysteine/serine proteases, DLH has a catalytic triad (Cys-123, His-202, Asp-171) and its mechanism probably involves the formation of covalently bound acyl intermediate via a tetrahedral intermediate. Unlike the proteases, DLH seems to protonate the incipient leaving group only after the collapse of the first tetrahedral intermediate, rendering DLH incapable of hydrolyzing amide analogues of its ester substrate. In addition, the triad His probably does not protonate the leaving group (enolate) or deprotonate the water for deacylation; rather, the enolate anion abstracts a proton from water and, in doing so, supplies the hydroxyl for deacylation.

Transglutaminase factor XIII uses proteinase‐like catalytic triad to crosslink macromolecules

“…Recently published work on catalytic triad enzymes has shown amazing variation in both structure and function, particularly among the a//3 hydrolase enzymes (Ollis et al, 1992;Cheah et al, 1993). The observations presented here for factor XI11 and the entire family of enzymatic transglutaminases demonstrate the versatility of the catalytic triad as a common scaffold for a wide range of enzymatic catalyses ranging from rather nonspecific protein hydrolysis to specific crosslinking of biological macromolecules by the transglutaminase.…”

New Bacterial Pathway for 4- and 5-Chlorosalicylate Degradation via 4-Chlorocatechol and Maleylacetate in Pseudomonas sp. Strain MT1

“…Dehalogenation of 4-chloromuconolactone by MT1 trans-DLH may be expected to resemble the 4-fluoromuconolactone conversion observed with 3-oxoadipate enol-lactone hydolases and proteobacterial DLHs (42,43). Some of these enzymes were found to transform 4-fluoromuconolactone mainly to maleylacetate, and based on the reaction mechanism suggested by Cheah et al (9) for dienelactone hydrolysis by cis/trans-DLH of Pseudomonas sp. strain B13, one may expect that the enzyme nucleophile attacks the lactone carbonyl group (Fig.…”

A Product Analog Bound Form of 3-Oxoadipate-enol-Lactonase (PcaD) Reveals a Multifunctional Role for the Divergent Cap Domain

“…Sequence analysis indicates that these arginines (R138 and R157) are highly conserved among the PcaD homologs (3-ketoadipateenol-lactonases) and that there is precedence for this type of interaction in DLH where R81 and R206 were observed to interact with the carboxylate of the dienelactam ring. 37,38 It is noteworthy though that while both R138 and R157 in PcaD and R81 in DLH are located on α-helices, R206 is located on a loop region in DLH. To the best of our knowledge, other than PcaD and its homologs, only DLH and one other ABH family member, 39 related by an anionic substrate, are known to have a high positive charge density at the entrance to the substrate binding pocket.…”