Anaerobic degradation of trans-cinnamate and omega-phenylalkane carboxylic acids by the photosynthetic bacterium Rhodopseudomonas palustris: evidence for a beta-oxidation mechanism.
The mechanism responsible for the initial steps in the anaerobic degradation of trans-cinnamate and omega-phenylalkane carboxylates by the purple non-sulphur photosynthetic bacterium Rhodopseudomonas palustris was investigated. Phenylacetate did not support growth and there was a marked CO2 dependence for growth on acids with greater side-chain lengths. Here, CO2 was presumably acting as a redox sink for the disposal of excess reducing equivalents. Growth on benzoate did not require the addition of exogenous CO2. Aromatic acids with an odd number of side-chain carbon atoms (3-phenylpropionate, 5-phenylvalerate, 7-phenylheptanoate) gave greater apparent molar growth yields than those with an even number of side-chain carbon atoms (4-phenylbutyrate, 6-phenylhexanoate, 8-phenyloctanoate). HPLC analysis revealed that phenylacetate accumulated and persisted in the culture medium during growth on these latter compounds. Cinnamate and benzoate transiently accumulated in the culture medium during growth on 3-phenylpropionate, and benzoate alone accumulated transiently during the course of trans-cinnamate degradation. The transient accumulation of 4-phenyl-2-butenoic acid occurred during growth on 4-phenylbutyrate, and phenylacetate accumulated to a 1:1 molar stoichiometry with the initial 4-phenylbutyrate concentration. It is proposed that the initial steps in the anaerobic degradation of trans-cinnamate and the group of acids from 3-phenylpropionate to 8-phenyloctanoate involves beta-oxidation of the side-chain.
Elder
D J
DJ
Robert Hill Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, UK.
Morgan
P
P
Kelly
D J
DJ
D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D002245:Carbon Dioxide / Q000378:metabolism; D002264:Carboxylic Acids / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002934:Cinnamates / Q000378:metabolism*; D003470:Culture Media; D008401:Gas Chromatography-Mass Spectrometry; D010084:Oxidation-Reduction; D012241:Rhodopseudomonas / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet
D002264:Carboxylic Acids; D002934:Cinnamates; D003470:Culture Media; D002245:Carbon Dioxide