Premium
The molecular basis for the intramolecular migration (NIH shift) of the carboxyl group during para ‐hydroxybenzoate catabolism
Author(s) -
Zhao Huan,
Xu Ying,
Lin Shuangjun,
Spain Jim C.,
Zhou NingYi
Publication year - 2018
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.14094
Subject(s) - thioester , hydroxylation , stereochemistry , catabolism , substituent , hydroxamic acid , moiety , coenzyme a , enzyme , biochemistry , dna ligase , biology , chemistry , reductase
Summary The NIH shift is a chemical rearrangement in which a substituent on an aromatic ring undergoes an intramolecular migration, primarily during an enzymatic hydroxylation reaction. The molecular mechanism for the NIH shift of a carboxyl group has remained a mystery for 40 years. Here, we elucidate the molecular mechanism of the reaction in the conversion of para ‐hydroxybenzoate (PHB) to gentisate (GA, 2, 5‐dihydroxybenzoate). Three genes ( phgABC ) from the PHB utilizer Brevibacillus laterosporus PHB‐7a encode enzymes ( p ‐hydroxybenzoyl‐CoA ligase, p ‐hydroxybenzoyl‐CoA hydroxylase and gentisyl‐CoA thioesterase, respectively) catalyzing the conversion of PHB to GA via a route involving CoA thioester formation, hydroxylation concomitant with a 1, 2‐shift of the acetyl CoA moiety and thioester hydrolysis. The shift of the carboxyl group was established rigorously by stable isotopic experiments with heterologously expressed phgABC, converting 2, 3, 5, 6‐tetradeutero‐PHB and [carboxyl‐ 13 C]‐PHB to 3, 4, 6‐trideutero‐GA and [carboxyl‐ 13 C]‐GA respectively. This is distinct from the NIH shifts of hydrogen and aceto substituents, where a single oxygenase catalyzes the reaction without the involvement of a thioester. The discovery of this three‐step strategy for carboxyl group migration reveals a novel role of the CoA thioester in biochemistry and also illustrates the diversity and complexity of microbial catabolism in the carbon cycle.