Indole-3-carboxylate decarboxylase

Non-oxidafive novel aromatic acid decarboxylases, pyrrole-2-carboxylate decarboxylase and indole-3-carboxylate decarboxylase, were found in Bacillus... 

The carboxylafion of indole into indole-3-carboxylate was observed by the purified indole-3-carboxylate decarboxylase as well as by the whole cells. For the carboxylafion reaction, temperatures over 30°C were not appropriate. The activities at 10, 20, and 30°C were about the same. The activity was maximal at pH 8.0 (Tris-HCl buffer, 100 mM). As shown in Fig. 10, the resting cells of A. nicotianae F11612 also catalyzed the carboxylafion of indole efficiently in the reaction mixture containing 20 mM indole, 3M KHCO3, 100mM potassium phosphate buffer (pH 6.0) in a tightly closed reaction vessel. By 6h, 6.81 mM indole-3-carboxylic acid accumulated in the reaction mixture with a molar conversion yield of 34%. Compared to the carhoxylation of pyrrole by pyrrole-2-carboxylate decarboxylase, the lower value compared might derive from the lower solubility of indole in the reaction mixture. 

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 The E-X-P motif is also conserved in pyrrole-2-carboxylate decarboxylase and indole-3-carboxylate decarboxylase (unpublished data).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. ... 

The enzyme was found in Arthrobacter nicotianae FI1612 and several molds. Its activity was induced specifically by indole-3-carboxylate, but not by indole. The indole-3-carboxylate decarboxylase of A. nicotianae FI1612 catalyzed the nonoxidative decarboxylation of indole-3-carboxylate into indole, and efficiently carboxylated indole and 2-methyhndole by the reverse reactirai. 

Yoshida T, Fujita K, Nagasawa T (2002) Novel reversible indole-3-carboxylate decarboxylase catalyzing nonoxidative decarboxylation. Biosci Biotechnol Biochem 66(11) 2388-2394... 

---