4- HYDROXYBENZOATE DECARBOXYLASE

Zhang et al. isolated Clostridium hydroxybenzoicum containing two inducible 4-hydroxybenzoate decarboxylase and 3,4-dihydroxybenzoate decarboxylase that form phenol and catechol (1,2-dihydroxybenzene), respectively. The organism does not further metabolize phenol and catechol produced by these reactions. The carboxylation activities of the two purified decarboxylases are not... 

Studies on 4-hydroxybenzoate decarboxylase and 3,4-hydroxybenzoate decarboxylase have been restricted to obligate anaerobic bacteria, C. hydroxy-benzoicum Aside from the obligate anaerobic microorganism, C. hydroxy-benzoicum, very recently facultative anaerobic bacteria, Enterobacter cloacae strains exhibiting high 4-hydroxybenzoate decarboxylase or... 

Hydroxybenzoate decarboxylase (EC 4.1.1.61) of anaerobe C. hydroxyben-zoicum was purified and characterized for the first time. ° It has an apparent molecular mass of 350 kDa and consists of six identical subunits of 57kDa. The temperature optimum for the decarboxylation is approximately 50°C, the optimum pH being 5.6-6.2. The activation energy for decarboxylation of 4-hydroxybenzoate is 65kJmor (20-37°C). The enzyme also catalyzes the decarboxylation of... 

The occurrence of 4-hydroxybenzoate decarboxylase was also found in facultative anaerobic bacteria, E. cloacae P240, and the enzyme was purified and characterized. The activity of the cell-free extract of E. cloacae P240 was determined to be 13.7 ijumol min (mg protein) at 30°C, which was much higher than... 

The occurrence of 3,4-dihydroxybenzoate decarboxylase was also found widely in facultative anaerobes. Among them, Enterobacter cloacae P241 showed the highest activity of 3,4-hydroxybenzoate decarboxylase, and the activity of the cell-free extract of E. cloacae P241 was determined to be 0.629 p.mol min (mg protein) at 30°C, which was more than that of C. hydroxybenzoicum, 0.11 (xmol min mg protein)" at 25°C. The E. cloacae P241 enzyme has a molecular mass of 334 kDa and consists of six identical 50 kDa subunits. The value for 3,4-dihydroxybenzoate was 177 p.M. The enzyme is also characteristic of its narrow substrate specificity and does not act on 4-hydroxybenzoate and other benzoate derivatives. The properties of E. cloacae P241 3,4-hydroxybenzoate decarboxylase were similar to those of C. hydroxybenzoicum in optimum temperature and pH, oxygen sensitivity, and substrate specificity. 

The purified E. cloacae P240 4-hydroxybenzoate decarboxylase did not catalyze the carboxylation of phenylphosphate, indicating phenolphosphate... 

Dihydroxybenzoate decarboxylase activity of these bacteria was induced specifically by 2,6-dihydroxybenzoate. The enzyme activity in a cell-free extract of A. tumefaciens 1AM 12048 was stable during storage at 4°C for 7 days in potassium phosphate buffer (pH 7.0) containing 1 mM dithiothreitol. Different from 4-hydroxybenzoate decarboxylase and 3,4-dihydroxybenzoate decarboxylase, 2,6-dihydroxybenzoate decarboxylase was much less labile and barely... 

Class I 4-Hydroxybenzoate Chyd 57 3-Octaprenyl-4-hydroxybenzoate decarboxylase... 

In the aligned primary structures of class I decarboxylases, the conserved amino acid residues are scattered over their primary structures. There have been few reports to identify the amino acid residues essential for catalytic activity or substrate binding. Huang et al. reported the E-X-P motif in the alignment analysis for 4-hydroxybenzoate decarboxylase of C. hydroxybenzoicum and its homologous unidentified proteins. The E-X-P motif is also conserved in pyrrole-2-carboxylate decarboxylase and indole-3-carboxylate decarboxylase (unpublished data). However, the corresponding motif sequence is not observed in the primary structures of 3,4-dihydroxybenzoate decarboxylase of E. cloacae P241. ... 

Primary structure analysis of phenylphosphate carboxylase of T. aromatica is performed in detail, to clarify the reaction mechanism involving four kinds of subunits. The a, (3, y, 8 subunits have molecular masses of 54, 53, 18, and lOkDa, respectively, which make up the active phenylphosphate carboxylase. The primary structures of a and (3 subunits show homology with 3-octaprenyl-4-hydroxybenzoate decarboxylase, 4-hydroxybenzoate decarboxylase, and vanil-late decarboxylase, whereas y subunit is unique and not characterized. The 18kDa 8 subunit belongs to a hydratase/phosphatase protein family. Taking 4-hydroxybenzoate decarboxylase into consideration, Schiihle and Fuchs postulate that the a(3y core enzyme catalyzes the reversible carboxylation. ... 

Huang, J., Z. He, and J. Wiegel, Cloring, characterization, and expression of a novel gene encoding a reversible 4-hydroxybenzoate decarboxylase from Clostridium hydroxybenzoicum , J. Bacteriol., 181, 5119-5122 (1999). 

The conversion of 3-octaprenyl-4-hydroxybenzoate (49) to 2-octaprenylphenol (50) was demonstrated by Cox et The enzyme responsible for this conversion was named 3-octaprenyl-4-hydroxybenzoate decarboxylase. The presence of a decarboxylase was also observed by El Hachimi et al This enzyme activity was absent in ubiD mutants. " ... 

An alternate 3-octaprenyl-4-hydroxybenzoate decarboxylase encoded by the uhiX gene has been described in S. typhimurium, which carries out the same reaction as the fo D-encoded enzyme. " An ubiX gene showing 70% homology to the S. typhimurium gene has been identified in E. The orjk encoding the two enzymes... 

Figure 17 Proposed mechanism for 3-octaprenyl-4-hydroxybenzoate decarboxylase reaction.

Various enzymes are known to catalyze arene carboxylation or decarboxylation in nature [41]. The first report [42] of a preparatively useful biocatalytic arene carboxylation was the para-carboxylation of phenol using the enzyme phenyl phosphate carboxylase. As the name imphes, this requires the phenol to be phosphorylated prior to reaction. Subsequently, phenol para-carboxylation without prior phosphorylation was demonstrated using enzymes such as 4-hydroxybenzoate decarboxylase [43-45] and 3,4-dihydroxybenzoate decarboxylase [46, 47] (Scheme 32.10). Although the natural function of these latter enzymes is to catalyze catalyze reactions in either direction, dependent on the reaction conditions. 

J., Purification and characterization of an oxygen-sensitive, reversible 3,4-dihydoxybenzoate decarboxylase from Clostridium hydroxybenzoicum, Eur. J. Biochem., 1995,229,77—82 (f) He, Z. and Wiegel, J., Purification and characterization of an oxygen sensitive reversible 4 hydroxybenzoate decarboxylase from Clostridium hydroxybenzoicum, J. BacterioL, 1996, 178(12), 3539-3543. 

He Z, Wiegel J (1995) Purification and characterization of an oxygen-sensitive reversible 4-hydroxybenzoate decarboxylase from Clostridium hydroxybenzoicum. Eur J Biochem 229 77-82... 

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