| Abstrakt: |
Dienelactone hydrolase (DLH) was purified to electrophoretic homogeneity from the biomass of the Pseudomonas putida strain 87 grown on 3-chlorobenzoate. The specific activity of the purified enzyme is 50.5 U./mg of protein. The enzyme is a monomer with a molecular mass of 22 kDa, has a pH optimum at 7.6 and is active within a broad temperature range (20-45 degrees C). The enzyme activity is inhibited by pCMB (which requires up to two equivalents of the reagent) but not by EDTA. The Vmax values of DLH for trans-dienelactone and 2-chlorodienelactone are practically identical (247.9 and 247 u./mg, respectively) and exceeded two fold that for cis-dienelactone. However, the Km for 2-chlorodienelactone is two times as high as that for trans-dienelactone (6.9 and 14.2 microM, respectively). A comparison of physico-chemical and kinetic properties of P. putida 87 DLH with those of the enzymes responsible for the decomposition of chlorinated and fluorinated compounds revealed that the enzyme can be assigned to the third group, i.e., the DLH-modified ortho-cleavage path way characteristic of gram-negative bacteria. |
