5CGZ

Crystal structure of GalB, the 4-carboxy-2-hydroxymuconate hydratase, from Pseuodomonas putida KT2440

Summary for 5CGZ

• Entry DOI: 10.2210/pdb5cgz/pdb
• Descriptor: 4-oxalmesaconate hydratase, ZINC ION, GLYCEROL, ... (4 entities in total)
• Functional Keywords: galb, hydratase, metalloenzyme, rossmann fold, helical hairpin, gallic acid, hexamer, lyase
• Biological source: Pseudomonas putida (strain KT2440)
• Total number of polymer chains: 2
• Total formula weight: 55717.81

Authors

Mazurkewich, S.,Brott, A.S.,Kimber, M.S.,Seah, S.Y.K. (deposition date: 2015-07-09, release date: 2016-02-17, Last modification date: 2024-03-06)

Primary citation

Mazurkewich, S.,Brott, A.S.,Kimber, M.S.,Seah, S.Y.
Structural and Kinetic Characterization of the 4-Carboxy-2-hydroxymuconate Hydratase from the Gallate and Protocatechuate 4,5-Cleavage Pathways of Pseudomonas putida KT2440.
J.Biol.Chem., 291:7669-7686, 2016

PubMed Abstract: The bacterial catabolism of lignin and its breakdown products is of interest for applications in industrial processing of ligno-biomass. The gallate degradation pathway ofPseudomonas putidaKT2440 requires a 4-carboxy-2-hydroxymuconate (CHM) hydratase (GalB), which has a 12% sequence identity to a previously identified CHM hydratase (LigJ) fromSphingomonassp. SYK-6. The structure of GalB was determined and found to be a member of the PIG-LN-acetylglucosamine deacetylase family; GalB is structurally distinct from the amidohydrolase fold of LigJ. LigJ has the same stereospecificity as GalB, providing an example of convergent evolution for catalytic conversion of a common metabolite in bacterial aromatic degradation pathways. Purified GalB contains a bound Zn(2+)cofactor; however the enzyme is capable of using Fe(2+)and Co(2+)with similar efficiency. The general base aspartate in the PIG-L deacetylases is an alanine in GalB; replacement of the alanine with aspartate decreased the GalB catalytic efficiency for CHM by 9.5 × 10(4)-fold, and the variant enzyme did not have any detectable hydrolase activity. Kinetic analyses and pH dependence studies of the wild type and variant enzymes suggested roles for Glu-48 and His-164 in the catalytic mechanism. A comparison with the PIG-L deacetylases led to a proposed mechanism for GalB wherein Glu-48 positions and activates the metal-ligated water for the hydration reaction and His-164 acts as a catalytic acid.

PubMed: 26867578
DOI: 10.1074/jbc.M115.682054

Experimental method

X-RAY DIFFRACTION (2.103 Å)