Publications

• The crystal structure of HpcE, a bifunctional decarboxylase/isomerase with a multifunctional fold.

  Tame J.R.H., Namba K., Dodson E.J., Roper D.I.

  The structure of the bifunctional enzyme HpcE (OPET decarboxylase/HHDD isomerase) from Escherichia coli shows that the protein consists of highly similar N and C terminal halves. Sequence matches suggest that this fold is widespread among different species, including man. Many of these homologues ... >> More

  The structure of the bifunctional enzyme HpcE (OPET decarboxylase/HHDD isomerase) from Escherichia coli shows that the protein consists of highly similar N and C terminal halves. Sequence matches suggest that this fold is widespread among different species, including man. Many of these homologues are uncharacterized but apparently connected with the metabolism of aromatic compounds. The domain shows similar topology to the C terminal domain of fumarylacetoacetate hydrolase (FAH), a functionally related enzyme, despite lacking significant overall sequence similarity. HpcE is known to catalyze two rather different reactions, and comparisons with FAH allow some tentative conclusions to be drawn about the active sites. Key mutations within the active site apparently allow enzymes with this fold to carry out a variety chemical processes. << Less

  Biochemistry 41:2982-2989(2002) [PubMed] [EuropePMC]

• Purification, some properties and nucleotide sequence of 5-carboxymethyl-2-hydroxymuconate isomerase of Escherichia coli C.

  Roper D.I., Cooper R.A.

  As part of an investigation into the evolution of catabolic pathway enzymes a cloned gene encoding the Escherichia coli C 5-carboxymethyl-2-hydroxymuconate (CHM) isomerase, an enzyme of the homoprotocatechuate catabolic pathway, was used to produce large amounts of the protein. The isomerase was p ... >> More

  As part of an investigation into the evolution of catabolic pathway enzymes a cloned gene encoding the Escherichia coli C 5-carboxymethyl-2-hydroxymuconate (CHM) isomerase, an enzyme of the homoprotocatechuate catabolic pathway, was used to produce large amounts of the protein. The isomerase was purified to homogeneity and some of its properties determined. The reaction occurred optimally at pH 7.6 and the specificity constant was 5.8 x 10(5) M-1.s-1 with CHM and 6.0 x 10(2) M-1.s-1 with 2-hydroxyhepta-2,4-diene-1,7-dioate, the substrate of a second isomerase in the pathway. The pure protein showed one type of subunit of Mr 14,000 whilst the molecular mass of the native enzyme was 30,000, suggesting that it was a dimer of identical subunits. The first 19 N-terminal amino acids were sequenced and the data used to confirm that the open reading frame of 378 bp, identified from the nucleotide sequence, encoded the CHM isomerase. << Less

  FEBS Lett. 266:63-66(1990) [PubMed] [EuropePMC]

• Purification, nucleotide sequence and some properties of a bifunctional isomerase/decarboxylase from the homoprotocatechuate degradative pathway of Escherichia coli C.

  Roper D.I., Cooper R.A.

  A 1.8-kbp region of DNA that appeared from deletion subcloning to code for 2-hydroxyhepta-2,4-diene-1,7-dioate isomerase and 5-oxopent-3-ene-1,2,5-tricarboxylate decarboxylase was investigated further. By nucleotide sequencing, a single open reading frame was found encoding a polypeptide of M(r)44 ... >> More

  A 1.8-kbp region of DNA that appeared from deletion subcloning to code for 2-hydroxyhepta-2,4-diene-1,7-dioate isomerase and 5-oxopent-3-ene-1,2,5-tricarboxylate decarboxylase was investigated further. By nucleotide sequencing, a single open reading frame was found encoding a polypeptide of M(r)44514. One of the deletion subclones expressed the decarboxylase and isomerase activities at elevated levels and was used to facilitate purification of the enzyme(s). Both activities copurified, indicating that they were distinct activities of the same protein. Some kinetic properties of the purified isomerase/decarboxylase protein were investigated and it was shown that there is a 49,000-fold preference for 2-hydroxyhepta-2,4-diene-1,7-dioate over the structurally related compound 5-carboxymethyl-2-hydroxymuconate, the substrate of a second isomerase in the same catabolic pathway. Comparison of the amino acid sequences of the two isomerases showed only a low level of similarity, suggesting that these two enzymes are not evolutionarily related. However, comparison of the N-terminal half of the isomerase/decarboxylase sequence (residues 1-202) with the second half (residues 203-406) showed significant similarity, suggesting that a duplication may have occurred to produce the bifunctional gene. << Less

  Eur. J. Biochem. 217:575-580(1993) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Identification and purification of distinct isomerase and decarboxylase enzymes involved in the 4-hydroxyphenylacetate catabolic pathway of Escherichia coli.

  Garrido-Peritierra A., Cooper R.A.

  The possible involvement of an isomerase in the 4-hydroxyphenylacetate meta-cleavage pathway has been studied. 5-Carboxymethyl-2-hydroxymuconate has been shown to undergo both spontaneous and enzyme-catalysed isomerisation to give 5-carboxymethyl-2-oxo-hex-3-ene-1,5-dioate, a compound with an abso ... >> More

  The possible involvement of an isomerase in the 4-hydroxyphenylacetate meta-cleavage pathway has been studied. 5-Carboxymethyl-2-hydroxymuconate has been shown to undergo both spontaneous and enzyme-catalysed isomerisation to give 5-carboxymethyl-2-oxo-hex-3-ene-1,5-dioate, a compound with an absorbance maximum at 246 nm. The latter compound rather than the former is the substrate for a decarboxylase that produces 2-hydroxyhepta-2,4-diene,1,7-dioate. The isomerase and decarboxylase enzymes have been purified to over 90% homogeneity. Mg2+ is required for the decarboxylase reaction but not for the isomerase. << Less

  Eur J Biochem 117:581-584(1981) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.