1.13.12.19: 2-oxoglutarate dioxygenase (ethene-forming)

-

764978, 765536

-

?

in the other reaction [EC 1.14.20.7, 2-oxoglutarate/L-arginine monooxygenase/decarboxylase (succinate-forming)] the enzyme catalyses the mono-oxygenation of both 2-oxoglutarate and L-arginine, forming succinate, carbon dioxide and L-hydroxyarginine, which is subsequently cleaved into guanidine and (S)-1-pyrroline-5-carboxylate. An iron(IV)-oxo intermediate initiates L-arginine oxidation but not ethylene production by the 2-oxoglutarate-dependent oxygenase, ethylene-forming enzyme

764978

-

?

in the other reaction [EC 1.14.20.7, 2-oxoglutarate/L-arginine monooxygenase/decarboxylase (succinate-forming)] the enzyme catalyses the mono-oxygenation of both 2-oxoglutarate and L-arginine, forming succinate, carbon dioxide and L-hydroxyarginine, which is subsequently cleaved into guanidine and (S)-1-pyrroline-5-carboxylate. The reaction mechanism of the enzyme (EFE) is studied with QM/MM methods. Based on the results, a branched pathway for the enzyme that can lead either to ethylene or to succinate via L-Arg hydroxylation is proposed. After formation of the Fe-O2 species, the nucleophilic attack of distal oxygen on the keto carbon of 2-oxoglutarate is accompanied by the breaking of the C1-C2 bond in 2-oxoglutarate, leading to an FeII-peroxysuccinate complex with a dissociated CO2. This FeII-peroxysuccinate species serves as the branch point intermediate in the dual transformations by EFE. It can proceed in two directions. In one branch, the subsequent O-O bond cleavage generates the succinate-bound FeIV-oxo intermediate. Next a nearby water molecule binds to the iron to form a hexacoordinated FeIV-oxo intermediate. Hydrogen atom abstraction from L-Arg, hydroxyl radical rebound, and elimination of guanidine from the hydroxylated L-Arg product complete the cycle. This represents the well-established mechanism for substrate oxidation by Fe/2OG oxygenases. Alternatively, starting from FeII-peroxysuccinate, the CO2 insertion into the Fe-O bond gives a peroxic anhydride species. Further steps, including the water binding, O-O bond cleavage, intermolecular proton transfer, and two consecutive C-C bond breaking steps, result in the formation of ethylene. According to the proposed reaction mechanism of EFE, a competition between the CO2 insertion and the O-O bond cleavage from the branch point intermediate governs the product selectivity. The calculated reaction barriers show a preference for the CO2 insertion reaction

765536

-

?

-

764156

-

?

2-oxoglutarate + O2

ethylene + 3 CO2 + H2O

-

741936, 742750, 743692, 744563

-

?

Q549K5

-

743235

-

?

ethylene forming reaction

-

?

Pseudomonas savastanoi pv. phaseolicola PK2

the enzyme is dependent on 2-oxoglutarate

743692

-

?

-

741936, 742750

-

?

ethylene forming reaction

-

?

Q549K5

-

743235

-

?

-

728247, 744558

-

?

-

715773

-

?

Pseudomonas syringae pv. pisi

enzyme is highly specific for substrate 2-oxoglutarate

715784

-

?

Q9Z3T0

-

744563

-

?

3 2-oxoglutarate + L-arginine + 3 O2

2 C2H4 + succinate + 7 CO2 + 3 H2O + guanidine + L-DELTA1-pyrroline-5-carboxylate

Penicillium digitatum

-

cf. EC 1.14.11.34

Pseudomonas savastanoi pv. glycinea

-

?

Q7BS32

cf. EC 1.14.11.34

-

?

cf. EC 1.14.11.34

-

?

cf. EC 1.14.11.34, reaction, mechanism of the two reaction catalyzed at the same time, overview. Enzyme EFE converts 2-oxoglutarate into ethylene plus three CO2 molecules while also catalyzing the C5 hydroxylation of L-arginine driven by the oxidative decarboxylation of 2-oxoglutarate to form succinate and CO2

Pseudomonas savastanoi pv. phaseolicola PK2

-

?

cf. EC 1.14.11.34, reaction, mechanism of the two reaction catalyzed at the same time, overview. Enzyme EFE converts 2-oxoglutarate into ethylene plus three CO2 molecules while also catalyzing the C5 hydroxylation of L-arginine driven by the oxidative decarboxylation of 2-oxoglutarate to form succinate and CO2

-

?

cf. EC 1.14.11.34

-

?

-

cf. EC 1.14.11.34

744558

-

?

Ralstonia solanacearum

Q8XPV7

cf. EC 1.14.11.34

-

?

additional information

?

-

cf. EC 1.14.11.34, reaction via 5-hydroxyarginine. Selected L-Arg derivatives induce ethylene formation without undergoing hydroxylation, demonstrating that ethylene production and L-Arg hydroxylation activities are not linked. Enzyme EFE utilizes the alternative 2-oxo acid 2-oxoadipate as a cosubstrate (forming glutaric acid) during the hydroxylation of L-Arg, with this reaction unlinked from ethylene formation. The amount of ethylene produced is more than twice the levels of succinate, L-DELTA1-pyrroline-5-carboxylate, or guanidine generated

741936

-

?

Pseudomonas syringae ethylene-forming enzyme reveal a branched mechanism. In one branch, an apparently typical 2-oxoglutarate oxygenase reaction to give succinate, carbon dioxide, and sometimes pyrroline-5-carboxylate occurs, reaction of EC 1.13.11.34. Alternatively, Grob-type oxidative fragmentation of a 2-oxoglutarate-derived intermediate occurs to give ethylene and carbon dioxide, EC 1.13.12.19. Fragmentation to give ethylene is promoted by binding of L-arginine in a nonoxidized conformation and of 2-oxoglutarate in an unprecedented high-energy conformation that favors ethylene, relative to succinate formation. Role for Tyr192 in catalysis, substrate binding structures, structure-function analysis, overview

743692

-

?

substrate binding structures, crystal structure analysis, overview. In all cases of bound 2-oxoglutarate, the carboxylate distal to the metal is stabilized by a salt bridge with R277, and the carboxylate coordinating the metal is stabilized by hydrogen bonds with R171. The C1-carboxylate oxygen of 2-oxoglutarate binds approximately trans to the distal H268 and the C2-oxo oxygen binds opposite D191. L-Arg binds near, but does not coordinate, the metal center in EFE-Mn-2OG-L-Arg

Pseudomonas savastanoi pv. phaseolicola PK2

-

?

cf. EC 1.14.11.34, reaction via 5-hydroxyarginine. Selected L-Arg derivatives induce ethylene formation without undergoing hydroxylation, demonstrating that ethylene production and L-Arg hydroxylation activities are not linked. Enzyme EFE utilizes the alternative 2-oxo acid 2-oxoadipate as a cosubstrate (forming glutaric acid) during the hydroxylation of L-Arg, with this reaction unlinked from ethylene formation. The amount of ethylene produced is more than twice the levels of succinate, L-DELTA1-pyrroline-5-carboxylate, or guanidine generated

741936

-

?

substrate binding structures, crystal structure analysis, overview. In all cases of bound 2-oxoglutarate, the carboxylate distal to the metal is stabilized by a salt bridge with R277, and the carboxylate coordinating the metal is stabilized by hydrogen bonds with R171. The C1-carboxylate oxygen of 2-oxoglutarate binds approximately trans to the distal H268 and the C2-oxo oxygen binds opposite D191. L-Arg binds near, but does not coordinate, the metal center in EFE-Mn-2OG-L-Arg

-

?

enzyme catalyzes the formation of ethylene and succinate from 2-oxoglutarate, at a molar ratio of 2:l, reactions of EC 1.13.12.19 and EC 1.14.11.34. In the main reaction, 2-oxoglutarate is dioxygenated to produce one molecule of ethylene and three molecules of carbon dioxide. In the sub-reaction, both 2-oxoglutarate and L-arginine are mono-oxygenated to yield succinate plus carbon dioxide and L-hydroxyarginine, respectively, the latter being further transformed to guanidine and L-delta-pyrroline-5-carboxylate. Dual-circuit mechanism for the entire reaction is proposed, in which the binding of L-arginine and 2-oxoglutarate in a Schiff-base structure generates a common intermediate for two reactions

714008

-

?