3,4-Protocatechuate structure

One last class of mononuclear non-haem iron enzyme that we have not yet considered, consists of the microbial superoxide dismutases with Fe(III) at their active site. The crystal structure of the E. coli enzyme shows a coordination geometry reminiscent of protocatechuate 3,4-dioxygenase, with four endogenous protein ligands, three His and one Asp residue, and one bound water molecule (Carlioz et ah, 1988). 

Figure 2 X-Ray structure of the site active of protocatechuate 3,4-dioxygenase from Pseudomonas aeruginosa...

A representative sampling of non-heme iron proteins is presented in Fig. 3. Evident from this atlas is the diversity of structural folds exhibited by non-heme iron proteins it may be safely concluded that there is no unique structural motif associated with non-heme iron proteins in general, or even for specific types of non-heme iron centers. Protein folds may be generally classified into several categories (i.e., all a, parallel a/)3, or antiparallel /8) on the basis of the types and interactions of secondary structures (a helix and sheet) present (Richardson, 1981). Non-heme iron proteins are found in all three classes (all a myohemerythrin, ribonucleotide reductase, and photosynthetic reaction center parallel a/)8 iron superoxide dismutase, lactoferrin, and aconitase antiparallel )3 protocatechuate dioxygenase, rubredoxins, and ferredoxins). This structural diversity is another reflection of the wide variety of functional roles exhibited by non-heme iron centers. 

Borbulevych, O.Y. et al.. Lipoxygenase interactions with natural flavonoid, quercetin, reveal a complex with protocatechuic acid in its x-ray structure at 2.1 A resolution. Proteins, 54, 13, 2004. 

There is a substantial literature on the transformation of simple phenolic acids by microorganisms.2,7,11,16,18,20,22,25,29,44 For example, ferulic acid is transformed by fungi to either caffeic acid or vanillic acid, and these are transformed to protocatechuic acid. Next the ring structure of protocatechuic acid is broken to produce 3-carboxy-c/s,c/s-muconic acid, which is then converted to (3-oxoadipic acid (Fig. 3.1), which in turn is broken down to acetic acid and succinic acid, and these ultimately are broken down to C02 and water.11,18,29 Flowever, distribution of residual 14C-activity after growth of Hendersonula toruloidea, a fungus, in the presence of specifically 14C-labeled ferulic acid ranged from 32 to 45% in C02, 34 to 45% in cells, 9 to 20% in humic acid and 4 to 10% in fulvic acid.29 Thus, a considerable portion of the ferulic-acid carbon was bound/fixed over a 12-week period, and the initial ferulic acid transformation products (e.g., caffeic acid, vanillic acid and protocatechuic acid) were clearly of a transitory nature. Similar observations have also been made for other simple phenolic acids 22,23 however, the proportions metabolized to C02 and fixed into cells and the soil... 

V=9.267(1) nm, Z=4, Ri=0.0S3 and Rw=0,058. The complex is composed of copper cations, nitrate anions, 1,10-phenanthroline, protocatechuic acid and lattice water molecules. The structure of H3PCA, N03 and waters comprises packing of three-dimensional network by hydrogen bonds with cavities. The complex can be considered as a model of host/guest supermolecule. The three-dimensional hydrogen-bonding network is the host species. The Cu(phen)3 cations, guest species, occupy the cavities of the host. 

Scheme 1 Structural forms of protocatechuic acid and protocatechuates...

There are many enzymes in the functionally diverse enolase superfamUy. The overall structural features of these enzymes are similar to the enolase structures, with an aip barrel active domain and a smaller domain (left lower domain. Figure 13A) where the essential Mg(II) bound to two Asp and one Gin side chains on the third, fourth and fifth p strands. In some cases, however, the active domain is better described as an aip)jP barrel (e.g. Figure 14A). The enzymes in this superfamily include O-succinylbenzoate synthase, epimerases, racemases, the muconate and carboxy lactonizing enzymes (cycloiso-merases) in bioconversion of catechol and protocatechuate, respectively , acid-sugar... 

K. Sugimoto, T. Senda, H. Aoshima, E. Masai, M. Fukuda, and Y. Mitsui. 1999. Crystal structure of an aromatic ring opening dioxygenase LigAB, a protocatechuate 4,5-dioxygenase, under aerobic conditions Structure FoldDes. 1 953-965. (PubMed)... 

I). At the end of the 3-week incubation, there was a proportionate increase in the amount of 14C02 evolved and decrease in the soil-bound residues formed as the number of 2,4-dichlorophenol pretreatments increased (Table I). The potential of structurally similar compounds such as protocatechuic acid and vanillic acid in conditioning soils for rapid degradation of 2,4-D has been documented (23). 

A view of the active site of protocatechuate 3,4-dioxygenase based on the results of the x-ray crystal structure. The Fe center is approximately trigonal bipyramidal, with Tyr-147 and His-162 as axial ligands, and Tyr-108 and His-160 in the equatorial plane along with a solvent molecule (not shown) in the foreground. ... 

Subunit Structure of Enzyme, Determination of the N-terminal amino acid in metapyrocatechase revealed that it contains about 2 moles of serine per mole of the enzyme, indicating that the enzyme consists of at least two peptide chains. Ultracentrifugal and diffusion analyses of the enzyme suggested that it was dissociated in 0.03N NaOH into two to three subunits. Likewise, protocatechuate 3,4-dioxygenase (19.4 ) was dissociated into small subunits (5.0s) in 0.05N NaOH, and electron microscope observation of the enzyme suggested that it consists of eight subunits. 

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