PURIFICATION AND SOME PROPERTIES OF 2-HYDROXYCHROMENE-2-CARBOXYLATE ISOMERASE FROM NAPHTHALENESULFONATE-ASSIMILATING PSEUDOMONAS SP. TA-2

A 2-hydroxychromene-2-carboxylate isomerase was purified from a cell-f ree extract of naphthalenesulfonate-assimilating Pseudomonas sp. TA-2 to an electrophoretically homogeneous state by successive column chrom atography on DEAE-cellulose, DEAE-Toyopearl 650M, Sephadex G-75, Hydro xyapatite, and Mono Q. The enzyme had a molecular mass of 25 and 27 kD a as estimated by SDS-PAGE and Superdex 200, respectively. Its N-termi nal 30 amino acid sequence had high homology with the deduced amino ac id sequences of the 2HC2CA isomerase of nahD (a gene of naphthalene me tabolism), pahD (a gene of naphthalene and phenanthrene metabolism), a nd doxJ (a gene of dibenzothiophene metabolism). The enzymatic product was a traits isomer, The isomerase activity was inhibited in the pres ence of monoiodoacetate or Hg2+, but not by preincubation with monoiod oacetate or N-ethylmaleimide, GSH functioned as a cofactor and activat ed the enzyme at above 0.15 mM.