Xenobiotic phthalates are industrially produced on the annual million ton scale. The oxygen-independent enzymatic reactions involved in anaerobic phthalate degradation have only recently been elucidated. In vitro assays suggested that phthalate is first activated to phthaloyl-CoA followed by decarboxylation to benzoyl-CoA. Here, we report the heterologous production and characterization of the enzyme initiating anaerobic phthalate degradation from 'Aromatoleum aromaticum': a highly specific succinyl-CoA:phthalate CoA transferase (SPT, class III CoA transferase). Phthaloyl-CoA formed by SPT accumulated only to sub-micromolar concentrations due to the extreme lability of the product towards intramolecular substitution with a half-life of around 7 min. Upon addition of excess phthaloyl-CoA decarboxylase (PCD), the combined activity of both enzymes was drastically shifted towards physiologically relevant benzoyl-CoA formation. In conclusion, a massive overproduction of PCD in phthalate-grown cells to concentrations >140 μM was observed that allowed for efficient phthaloyl-CoA conversion at concentrations 250-fold below the apparent K -value of PCD. The results obtained provide insights into an only recently evolved xenobiotic degradation pathway where a massive cellular overproduction of PCD compensates for the formation of the probably most unstable CoA ester intermediate in biology.

Some effects of the xylanase treatment on the separate birch ORGANOSOLV pulp fibre wall morphological layers were examined. These investigations were focused on the outer layers, i.e. the primary wall (P) and the outer layer of the secondary wall (Sl), as well as the central layers, i.e. the central layer of the secondary wall (Sz) and the tertiary wall (T).Step by step, the fractionation of the pulp components in the polar solvents N,N-dimethylfomamide (DMFA). dimethylsulphoxide (DMSO) and DMSO/H3P04 was used as a mild technique for $e isolation of the lignin-carbohydrate complexes.The different residual amounts of lignin and hemicelluloses in the outer and central pulp fibre wall layers as well as the different lignin-hemicellulose ratios were determined. The size-exclusion chromatographical (SEC) analysis showed a higher initial Iignin content in the region of the high molecular mass (MM) fibre wall fraction extracted with "DMSOI H3PO; than the outer cell wall layers. In the central layers, the amounts of soluble lignin (calculated on the mass of total dissolved substance) were approximately the same for all the three solvents.The xylanase treatment brought the most considerable changes in the high MM part of the residual lignin (the lignin carbohydrate complex). This was true for both the P-S, and S2-T layers. The careful brightness comparison of the outer and central fractions after the X-E-P-P bleaching sequence showed a surprisingly low bleachability of the outer layer fraction. The xylanase action depended on the composition of the lignin-carbohydrate complex (LCC) and the extent of the maintenance of the outer layers during the pulping process. 1832-1 837.