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5T2K

Geobacillus stearothermophilus HemQ with Manganese-Coproporphyrin III

Summary for 5T2K
Entry DOI10.2210/pdb5t2k/pdb
DescriptorPutative heme-dependent peroxidase GT50_08830, [3,3',3'',3'''-(3,8,13,17-tetramethylporphyrin-2,7,12,18-tetrayl-kappa~4~N~21~,N~22~,N~23~,N~24~)tetra(propanoato)(2-)]manganese (3 entities in total)
Functional Keywordshemq, coproporphyrin iii, decarboxylation, oxidoreductase
Biological sourceGeobacillus stearothermophilus 10
Total number of polymer chains5
Total formula weight147626.20
Authors
Gauss, G.H.,Celis, A.I.,Dubois, J.L.,Peters, J.W. (deposition date: 2016-08-23, release date: 2017-01-18, Last modification date: 2023-10-04)
Primary citationCelis, A.I.,Gauss, G.H.,Streit, B.R.,Shisler, K.,Moraski, G.C.,Rodgers, K.R.,Lukat-Rodgers, G.S.,Peters, J.W.,DuBois, J.L.
Structure-Based Mechanism for Oxidative Decarboxylation Reactions Mediated by Amino Acids and Heme Propionates in Coproheme Decarboxylase (HemQ).
J. Am. Chem. Soc., 139:1900-1911, 2017
Cited by
PubMed Abstract: Coproheme decarboxylase catalyzes two sequential oxidative decarboxylations with HO as the oxidant, coproheme III as substrate and cofactor, and heme b as the product. Each reaction breaks a C-C bond and results in net loss of hydride, via steps that are not clear. Solution and solid-state structural characterization of the protein in complex with a substrate analog revealed a highly unconventional HO-activating distal environment with the reactive propionic acids (2 and 4) on the opposite side of the porphyrin plane. This suggested that, in contrast to direct C-H bond cleavage catalyzed by a high-valent iron intermediate, the coproheme oxidations must occur through mediating amino acid residues. A tyrosine that hydrogen bonds to propionate 2 in a position analogous to the substrate in ascorbate peroxidase is essential for both decarboxylations, while a lysine that salt bridges to propionate 4 is required solely for the second. A mechanism is proposed in which propionate 2 relays an oxidizing equivalent from a coproheme compound I intermediate to the reactive deprotonated tyrosine, forming Tyr. This residue then abstracts a net hydrogen atom (H) from propionate 2, followed by migration of the unpaired propionyl electron to the coproheme iron to yield the ferric harderoheme and CO products. A similar pathway is proposed for decarboxylation of propionate 4, but with a lysine residue as an essential proton shuttle. The proposed reaction suggests an extended relay of heme-mediated e/H transfers and a novel route for the conversion of carboxylic acids to alkenes.
PubMed: 27936663
DOI: 10.1021/jacs.6b11324
PDB entries with the same primary citation
Experimental method
X-RAY DIFFRACTION (1.8 Å)
Structure validation

237735

数据于2025-06-18公开中

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