2-Hydroxychromene-2-carboxylate isomerase from bacteria that degrade naphthalenesulfonates

2-Hydroxychromene-2-carboxylate isomerase activity was found in cell-free systems from bacteria that degrade naphthalenesulfonates. The enzyme fromPseudomonas testosteroni A3 was activated by incubation with glutathione, dithiothreitol or mercaptoethanol. The highest enzyme activity was found after preincubation of the enzyme with glutathione at alkaline pH-values. A highly purified enzyme preparation converted besides 2-hydroxychromene-2-carboxylate also 2-hydroxybenzo[g]chromene-2-carboxylate (the 2-hydroxychromene-2-carboxylate formed from 1,2-dihydroxyanthracen). The addition of various metal ions or EDTA did not significantly change the catalytic activity of the enzyme. A possible reaction mechanism is proposed.Abbreviations 2,5-DHCCA 2,5-dihydroxychromene-2-carboxylate - 2,6-DHCCA 2,6-dihydroxychromene-2-carboxylate - 1,2-DHN 1,2-dihydroxynaphthalene - GSH glutathione - 2HBCCA 2-hydroxybenzo[g]chromene-2-carboxylate - HBP 2-hydroxybenzalpyruvate - HBPA 2-hydroxybenzalpyruvate aldolase - 2HCCA 2-hydroxychromene-2-carboxylate - 2HCCAI 2-hydroxychromene-2-carboxylate isomerase - 2NS naphthalene-2-sulfonate - R_t retention time