STUDIA UBB CHEMIA, LVI, 4, 2011 (p. 49 - 54) A COMPUTATIONAL INVESTIGATION OF THE DECAY MECHANISM OF THE REACTION PRODUCT OF ANTHRANILATE DIOXYGENASE (ANTHRANILIC ACID DIOL) RADU SILAGHI-DUMITRESCU a, *, RADU GHINGA b ABSTRACT. Anthranilate diol is a non-aromatic dihydrodiol produced during the enzymatic degradation of anthranilate by anthranilate dioxygenase. The anthranilate diol is generally accepted to decompose spontaneously to catechol, thus regaining aromaticity. The present study employs density functional (DFT), Hartree- Fock (HF) and AM1 calculations to examine the mechanism of anthranilate diol decomposition. Keywords: anthranilate, anthranilate diol, Rieske dioxygenase, catechol, DFT INTRODUCTION Rieske dioxygenases (RDO) are non-heme iron enzymes catalyzing the cis-1,2 di-hydroxylation of aromatic substrates, producing non-aromatic dihydrodiols. Within this family of enzymes, anthranilate dioxygenase catalyzes the transformation of anthranilate (2-aminobenzoate) to the corresponding diol, which then further decomposes to catechol and regains its aromaticity as shown in Figure 1. COO - NH 3 + + O 2 dioxygenase COO - NH 3 + OH OH anthranilate anthranilate diol OH OH -CO 2 -NH 3 catechol Rieske Figure 1. The reaction catalyzed by anthranilate dioxygenase, followed by decomposition of the diol. a Universitatea Babeş-Bolyai, Facultatea de Chimie şi Inginerie Chimică, Str. Kogălniceanu, Nr. 1, RO-400084 Cluj-Napoca, Romania, * rsilaghi@chem.ubbcluj.ro b Grup Şcolar de Transporturi Auto “Henri Coandă”, Str. Mărăşeşti, Nr. 34, RO-310332 Arad, Romania, radughinga@gmail.com