Publication Details

Category Text Publication
Reference Category Journals
DOI 10.1002/elsc.200720198
Title (Primary) Activity and reaction mechanism of the initial enzymatic step specifying the microbial degradation of 2,4-dichlorophenoxyacetate
Author Müller, R.H.
Source Titel Engineering in Life Sciences
Year 2007
Department UMB
Volume 7
Issue 4
Page From 311
Page To 321
Language englisch
Keywords biodegradation; enzymes; herbicides; xenobiotics
Abstract The capability of Delftia acidovorans MC1010 (SdpA+, RdpA-) to degrade the herbicides 2,4-dichlorophenoxyacetate (2,4-D) and 4-chloro-2-methylphenoxyacetate (MCPA) was investigated in batch degradation experiments and interpreted in the light of the catalytic activity of the initial enzyme SdpA, an -ketoglutarate-dependent dioxygenase, catalyzing the cleavage of the ether bond. Dense inocula of this strain degraded high initial 2,4-D concentrations quickly to below the detection limit. The specific degradation rate became slower and the degradation remained incomplete when low initial biomass concentrations and/or 2,4-D concentrations were used. With low initial 2,4-D concentrations, the degradation rate became nearly concentration-independent. This effect was less pronounced with MCPA, a substrate that is more readily degraded by SdpA than 2,4-D. (S)-2-(2,4-dichlorophenoxy)propionate ((S)-2,4-DP), the favored substrate of SdpA used as comparison, was almost completely utilized under the various conditions. The observed differences were attributed to the easier regeneration of the essential co-substrate -ketoglutarate with MCPA and above all (S)-2,4-DP as a substrate compared to 2,4-D. Decreasing SdpA activity, which was observed during the starvation of MC1010, will contribute to the apparent recalcitrance of 2,4-D. Degradation of 2,4-D by Bradyrhizobium sp. RD5-C2, a strain initiating 2,4-D cleavage by a monooxygenase not requiring an organic intermediate as a co-substrate, proceeded to completion despite the approximately 20-fold lower degradation rates compared to those obtained with strain MC1010. However, lowering of biomass concentrations resulted in restricted degradation also with strain RD5-C2. The results were discussed in terms of the kind of co-substrate in the cleavage reaction, the availability of essential intracellular metabolites, and the cells' maintenance demands.
Persistent UFZ Identifier https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=2100
Müller, R.H. (2007):
Activity and reaction mechanism of the initial enzymatic step specifying the microbial degradation of 2,4-dichlorophenoxyacetate
Eng. Life Sci. 7 (4), 311 - 321 10.1002/elsc.200720198