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Query: EC:5.5.1.1 (muconate lactonizing enzyme)
 85 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mandelate racemase and muconate lactonizing enzyme are structurally homologous but catalyze different reactions, each initiated by proton abstraction from carbon. The structural similarity to mandelate racemase of a previously unidentified gene product was used to deduce its function as a galactonate dehydratase. In this enzyme superfamily that has evolved to catalyze proton abstraction from carbon, three variations of homologous active site architectures are now represented: lysine and histidine bases in the active site of mandelate racemase, only a lysine base in the active site of muconate lactonizing enzyme, and only a histidine base in the active site of galactonate dehydratase. This discovery supports the hypothesis that new enzymatic activities evolve by recruitment of a protein catalyzing the same type of chemical reaction.
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PMID:A functionally diverse enzyme superfamily that abstracts the alpha protons of carboxylic acids. 785 94

Rhodococcus rhodochrous NCIMB 13259 grows on styrene, toluene, ethylbenzene, and benzene as sole carbon sources. Simultaneous induction tests with cells grown on styrene or toluene showed high rates of oxygen consumption with toluene cis-glycol and 3-methylcatechol, suggesting the involvement of a cis-glycol pathway. 3-Vinylcatechol accumulated when intact cells were incubated with styrene in the presence of 3-fluorocatechol to inhibit catechol dioxygenase activity. Experiments with 18O2 showed that 3-vinylcatechol was produced following a dioxygenase ring attack. Extracts contained a NAD-dependent cis-glycol dehydrogenase, which converted styrene cis-glycol to 3-vinylcatechol. Both catechol 1,2- and 2,3-dioxygenase activities were present, and these were separated from each other and from the activities of cis-glycol dehydrogenase and 2-hydroxymuconic acid semialdehyde hydrolase by ion-exchange chromatography of extracts. 2-Vinylmuconate accumulated in the growth medium when cells were grown on styrene, apparently as a dead-end product, and extracts contained no detectable muconate cycloisomerase activity. 3-Vinylcatechol was cleaved by catechol 2,3-dioxygenase to give a yellow compound, tentatively identified as 2-hydroxy-6-oxoocta-2,4,7-trienoic acid, and the action of 2-hydroxymuconic acid semialdehyde hydrolase on this produced acrylic acid. A compound with the spectral characteristics of 2-hydroxypenta-2,4-dienoate was produced by the action of 2-hydroxymuconic acid semialdehyde hydrolase on the 2,3-cleavage product of 3-methylcatechol. Extracts were able to transform 2-hydroxypenta-2,4-dienoate and 4-hydroxy-2-oxopentanoate into acetaldehyde and pyruvate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolism of styrene by Rhodococcus rhodochrous NCIMB 13259. 801 10

The conversion of 2-chloro-cis,cis-muconate by muconate cycloisomerase from Pseudomonas putida PRS2000 yielded two products which by nuclear magnetic resonance spectroscopy were identified as 2-chloro- and 5-chloromuconolactone. High-pressure liquid chromatography analyses showed the same compounds to be formed also by muconate cycloisomerases from Acinetobacter calcoaceticus ADP1 and Pseudomonas sp. strain B13. During 2-chloro-cis,cis-muconate turnover by the enzyme from P. putida, 2-chloromuconolactone initially was the major product. After prolonged incubation, however, 5-chloromuconolactone dominated in the resulting equilibrium. In contrast to previous assumptions, both chloromuconolactones were found to be stable at physiological pH. Since the chloromuconate cycloisomerases of Pseudomonas sp. strain B13 and Alcaligenes eutrophus JMP134 have been shown previously to produce the trans-dienelactone (trans-4-carboxymethylene-but-2-en-4-olide) from 2-chloro-cis,cis-muconate, they must have evolved the capability to cleave the carbon-chlorine bond during their divergence from normal muconate cycloisomerases.
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PMID:Inability of muconate cycloisomerases to cause dehalogenation during conversion of 2-chloro-cis,cis-muconate. 802 Dec 23

Resting phenol-grown mycelia of the fungus Penicillium frequentans strain Bi 7/2 were shown to be capable of metabolizing various monohalogenated phenols as well as 3,4-dichlorophenol. 2,4.dichlorophenol could be metabolized in the presence of phenol as cosubstrate. In the first degradation step the halogenated phenols were oxidized to the corresponding halocatechols. Halocatechols substituted in para-position (4-halocatechols) were further degraded under formation of 4-carboxymethylenbut-2-en-4-olide. A partial dehalogenation took place splitting the ring system. 3-Halocatechols were cleaved to 2-halomuconic acids as dead end metabolites without a dehalogenation step. Dichlorophenols were only transformed to the corresponding catechols. In addition 3,5-dichloro-catechol was O-methylated to give two isomers of dichloroguiacol. The halogenated catechols with the exception of 4-fluorocatechol partly polymerized oxidatively in the culture fluid to form insoluble dark-brown products. The degradation of halophenols are due to the action of unspecific intracellular enzymes responsible for phenol catabolism (phenol hydroxylase, catechol-1,2-dioxygenase, muconate cycloisomerase I).
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PMID:Unspecific degradation of halogenated phenols by the soil fungus Penicillium frequentans Bi 7/2. 807 3

The absolute stereochemical courses of cis,cis-muconate lactonizing enzyme (MLE;EC 5.5.1.1) from Trichosporon cutaneum (TcMLE) and chloromuconate cycloisomerase (MLE II; EC 5.5.1.7) from Pseudomonas sp B13 have been determined from 1H NMR measurements. Both cycloisomerases convert cis,cis-muconate to (4S)-muconolactone by a syn lactonization, the absolute stereochemical outcome of which is identical to that observed with MLE from Pseudomonas putida. The regiochemical courses of cyclization of 3-halo-cis,cis-muconates by TcMLE and MLE II have been characterized and shown to differ in a halogen substituent dependent manner, suggesting at least a different active site architecture of the two MLEs. Moreover, the regiochemical preferences of MLE II and TcMLE parallel results previously observed for the nonenzymatic lactonization of the 3-halomuconates at pH 1-6 and in concentrated HCl, respectively, in which alternate mechanisms of cyclization were proposed [Pieken, W. A., & Kozarich, J. W. (1990) J. Org. Chem. 55, 3029-3035]. Complementary DNA clones encoding TcMLE have been isolated from phenol induced T. cutaneum cDNA using the polymerase chain reaction. The deduced amino acid sequence does not exhibit any similarity to that of MLE from P. putida. It does however, exhibit moderate sequence similarity (21% residue identity, 14 gaps) with 3-carboxy-cis,cis-muconate lactonizing enzyme (CMLE; EC 5.5.1.5) from Neurospora crassa, which catalyzes a regiochemically analogous and stereochemically identical lactonization reaction with 3-carboxymuconate. The limited data available suggest that the fungal CMLE and yeast MLE are representative of a unique class of eucaryotic cycloisomerases which have evolved convergently with the bacterial MLEs.
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PMID:Cis,cis-muconate lactonizing enzyme from Trichosporon cutaneum: evidence for a novel class of cycloisomerases in eucaryotes. 811 Aug 1

3-Carboxy-cis,cis-muconate lactonizing enzyme (CMLE; EC 5.5.1.5) from Neurospora crassa catalyzes the reversible gamma-lactonization of 3-carboxy-cis,cis-muconate by a syn-1,2 addition-elimination reaction. The stereochemical and regiochemical course of the reaction is (i) opposite that of CMLE from Pseudomonas putida (EC 5.5.1.2) and (ii) identical to that of cis,cis-muconate lactonizing enzyme (MLE; EC 5.5.1.1) from P. putida. In order to determine the mechanistic and evolutionary relationships between N. crassa CMLE and the procaryotic cycloisomerases, we have purified CMLE from N. crassa to homogeneity and determined its nucleotide sequence from a cDNA clone isolated from a p-hydroxybenzoate-induced N. crassa cDNA library. The deduced amino acid sequence predicts a protein of 41.2 kDa (365 residues) which does not exhibit sequence similarity with any of the bacterial cycloisomerases. The cDNA encoding N. crassa CMLE was expressed in Escherichia coli, and the purified recombinant protein exhibits physical and kinetic properties equivalent to those found for the isolated N. crassa enzyme. We also report that N. crassa CMLE possesses substantially reduced yet significant levels of MLE activity with cis,cis-muconate and, furthermore, does not appear to be dependent on divalent metals for activity. These data suggest that the N. crassa CMLE may represent a novel eucaryotic motif in the cycloisomerase enzyme family.
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PMID:3-Carboxy-cis,cis-muconate lactonizing enzyme from Neurospora crassa: an alternate cycloisomerase motif. 813 67

The biochemical characterization of the muconate and the chloromuconate cycloisomerases of the chlorophenol-utilizing Rhodococcus erythropolis strain 1CP previously indicated that efficient chloromuconate conversion among the gram-positive bacteria might have evolved independently of that among gram-negative bacteria. Based on sequences of the N terminus and of tryptic peptides of the muconate cycloisomerase, a fragment of the corresponding gene has now been amplified and used as a probe for the cloning of catechol catabolic genes from R. erythropolis. The clone thus obtained expressed catechol 1,2-dioxygenase, muconate cycloisomerase, and muconolactone isomerase activities. Sequencing of the insert on the recombinant plasmid pRER1 revealed that the genes are transcribed in the order catA catB catC. Open reading frames downstream of catC may have a function in carbohydrate metabolism. The predicted protein sequence of the catechol 1,2-dioxygenase was identical to the one from Arthrobacter sp. strain mA3 in 59% of the positions. The chlorocatechol 1,2-dioxygenases and the chloromuconate cycloisomerases of gram-negative bacteria appear to be more closely related to the catechol 1,2-dioxygenases and muconate cycloisomerases of the gram-positive strains than to the corresponding enzymes of gram-negative bacteria.
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PMID:Characterization of catechol catabolic genes from Rhodococcus erythropolis 1CP. 899 Feb 88

Transposon mutagenesis was performed by the method of conjugational transfer in order to identify and characterize genes encoding enzymes involved in the pathway of phenol utilization as a carbon source. Escherichia coli, which carries the Tn5-132, Was mated with Pseudomonas putida SM25 as a host. We selected a mutant that could not utilize phenol as a carbon source. Chromosomal integration of the transposon was confirmed by Southern analysis, successfully tagging the gene related to a phenol-utilizing pathway. By cell-free enzyme and genetic complementation assays, the inactivated enzyme through the mutation of the corresponding gene was identified as the catB gene, which encodes a cis,cis-muconate lactonizing enzyme.
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PMID:Tn5 tagging of the phenol-degrading gene on the chromosome of Pseudomonas putida. 908 63

The pca structural genes encode enzymes that participate in the conversion of protocatechuate to succinate and acetylcoenzyme A. A 3. 05-kb region of the Bradyrhizobium japonicum strain USDA110 genome has been characterized, which contains the pcaB, pcaD and pcaC genes. The predicted protein sequences of the three genes have extensive homologies with beta-carboxy-cis,cis-muconate cycloisomerase (PcaB), beta-ketodiapate enol-lactone hydrolase (PcaD), and gamma-carboxymuconolactone decarboxylase (PcaC), respectively, from Acinetobacter calcoaceticus and Pseudomonas putida. The DNA sequence revealed that the pca genes are probably arranged in a single transcriptional unit, pcaBDC, similar to that described in P. putida. A pcaB deletion mutant constructed by marker exchange mutagenesis lost the ability to use 4-hydroxybenzoate or protocatechuate as the only carbon source, demonstrating functionality of the characterized genes in catabolism of hydroxyaromatics by B. japonicum. Furthermore, 4-hydroxybenzoate and protocatechuate became toxic for the pcaB mutant, indicating that hydroxyaromatics catabolism serves both nutritional and detoxifying purposes.
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PMID:Characterization of Bradyrhizobium japonicum pcaBDC genes involved in 4-hydroxybenzoate degradation. 958 32

Two muconate cycloisomerases (MC I and MC II, EC 5.5.1.1) were purified to homogeneity from an aniline-grown Frateuria sp. ANA-18. MC I and MC II were similar in molecular mass, optimal pH, and pH stability but different in thermostability, and some other enzymatic properties. NH2-terminal amino acid sequences were different between the two isozymes, indicated that these are encoded by different genes. Different inducible production of MC I and MC II suggested that two catechol branches involved in the beta-ketoadipate pathway function in Frateuria sp. ANA-18.
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PMID:Purification and characterization of two muconate cycloisomerase isozymes from aniline-assimilating Frateuria species ANA-18. 969 94


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