Literature summary for 1.21.4.5 extracted from

Kiefer, P.M.; Copley, S.D.
Characterization of the initial steps in the reductive dehalogenation catalyzed by tetrachlorohydroquinone dehalogenase (2002), Biochemistry, 41, 1315-1322 .

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Protein Variants

Protein Variants	Comment	Organism
C13S	the mutant enzyme, which catalyzes the reaction only to the point at which Cys13 is required. The reaction proceeds by a rapid equilibrium random sequential kinetic mechanism. Substrate analogues that lack a second hydroxyl group cannot be turned over to products, although they can bind to the active site. The rate of the reaction is strongly influenced by the number of electron withdrawing substituents on the substrate. These findings are consistent with a mechanism that begins with ketonization of the deprotonated substrate to form 2,3,5,6-tetrachloro-4-hydroxycyclohexa-2,4-dienone, followed by 1,4-elimination of HCl to from trichlorobenzoquinone. Subsequently, trichlorobenzoquinone is attacked by glutathione to form a glutathione conjugate that, in the absence of Cys13, decomposes to a mixture of products, either at the active site or after release into solution	Sphingobium chlorophenolicum

Natural Substrates/ Products (Substrates)

Natural Substrates	Organism	Comment (Nat. Sub.)	Natural Products	Comment (Nat. Pro.)	Rev.	Reac.
2,3,5,6-tetrachlorohydroquinone + 2 glutathione	Sphingobium chlorophenolicum	the enzyme converts tetrachlorohydroquinone to trichlorohydroquinone and trichlorohydroquinone to dichlorohydroquinone. The enzyme is involved in degradation of pentachlorophenol, a widely used wood preservative	2,3,6-trichlorohydroquinone + Cl- + glutathione disulfide	-	?
2,3,6-trichlorohydroquinone + 2 glutathione	Sphingobium chlorophenolicum	the enzyme converts tetrachlorohydroquinone to trichlorohydroquinone and trichlorohydroquinone to dichlorohydroquinone. The enzyme is involved in degradation of pentachlorophenol, a widely used wood preservative	2,6-dichlorohydroquinone + Cl- + glutathione disulfide	-	?

Organism

Organism	UniProt	Comment	Textmining
Sphingobium chlorophenolicum	Q03520	-	-

Substrates and Products (Substrate)

Substrates	Comment Substrates	Organism	Products	Comment (Products)	Rev.	Reac.
2,3,5,6-tetrachlorohydroquinone + 2 glutathione	the enzyme converts tetrachlorohydroquinone to trichlorohydroquinone and trichlorohydroquinone to dichlorohydroquinone. The enzyme is involved in degradation of pentachlorophenol, a widely used wood preservative	Sphingobium chlorophenolicum	2,3,6-trichlorohydroquinone + Cl- + glutathione disulfide	-	?
2,3,5,6-tetrachlorohydroquinone + 2 glutathione	the enzyme converts tetrachlorohydroquinone to trichlorohydroquinone and trichlorohydroquinone to dichlorohydroquinone. The reaction proceeds by a rapid equilibrium random sequential kinetic mechanism. Substrate analogues that lack a second hydroxyl group cannot be turned over to products, although they can bind to the active site. The rate of the reaction is strongly influenced by the number of electron withdrawing substituents on the substrate. These findings are consistent with a mechanism that begins with ketonization of the deprotonated substrate to form 2,3,5,6-tetrachloro-4-hydroxycyclohexa-2,4-dienone, followed by 1,4-elimination of HCl to from trichlorobenzoquinone. Subsequently, trichlorobenzoquinone is attacked by glutathione to form a glutathione conjugate	Sphingobium chlorophenolicum	2,3,6-trichlorohydroquinone + Cl- + glutathione disulfide	-	?
2,3,6-trichlorohydroquinone + 2 glutathione	the enzyme converts tetrachlorohydroquinone to trichlorohydroquinone and trichlorohydroquinone to dichlorohydroquinone. The enzyme is involved in degradation of pentachlorophenol, a widely used wood preservative	Sphingobium chlorophenolicum	2,6-dichlorohydroquinone + Cl- + glutathione disulfide	-	?
2,3,6-trichlorohydroquinone + 2 glutathione	the enzyme converts tetrachlorohydroquinone to trichlorohydroquinone and trichlorohydroquinone to dichlorohydroquinone	Sphingobium chlorophenolicum	2,6-dichlorohydroquinone + Cl- + glutathione disulfide	-	?

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Release 2023.1 (January 2023)