Logan M S, Newman L M, Schanke C A, Wackett L P
Gray Freshwater Biological Institute, University of Minnesota, Navarre 55392.
Biodegradation. 1993;4(1):39-50. doi: 10.1007/BF00701453.
Cytochrome P-450CAM was shown to be the primary catalyst mediating reductive dehalogenation of polychlorinated ethanes by Pseudomonas putida G786. Under anaerobic conditions, the enzyme catalyzed reductive elimination reactions in vivo with the substrates hexachloroethane, pentachloroethane, and 1,1,1,2-tetrachlorethane; the products were tetrachloroethylene, trichloroethylene, and 1,1-dichloroethylene, respectively. In vivo reaction rates were determined. No reaction was observed with 1,1,2,2-tetrachloroethane or 1,1,1-trichloroethane. Purified cytochrome P-450CAM was used to measure dissociation constants of polychlorinated ethanes for the enzyme active site. Observed rates and dissociation constants were used to predict the course of a reaction with the three substrates simultaneously. Data obtained from experiments with P. putida G786 generally followed the simulated reaction curves. Oxygen suppressed the reductive dechlorination reactions and, in the case of 1,1,1,2-tetrachlorethane, 2,2,2-trichloroacetaldehyde was formed. Significant rates of reductive dechlorination were observed at 5% oxygen suggesting that these reactions could occur under partially aerobic conditions. These studies highlight the potential to use an aerobic bacterium, P. putida G786, under a range of oxygen tensions to reductively dehalogenate mixed wastes which are only degraded at very low rates by obligately anaerobic bacteria.
细胞色素P-450CAM被证明是恶臭假单胞菌G786介导多氯乙烷还原脱卤的主要催化剂。在厌氧条件下，该酶在体内催化六氯乙烷、五氯乙烷和1,1,1,2-四氯乙烷底物的还原消除反应；产物分别为四氯乙烯、三氯乙烯和1,1-二氯乙烯。测定了体内反应速率。未观察到1,1,2,2-四氯乙烷或1,1,1-三氯乙烷的反应。使用纯化的细胞色素P-450CAM测量多氯乙烷与酶活性位点的解离常数。观察到的反应速率和解离常数用于预测与三种底物同时发生的反应过程。从恶臭假单胞菌G786实验获得的数据通常遵循模拟反应曲线。氧气抑制还原脱氯反应，在1,1,1,2-四氯乙烷的情况下，会形成2,2,2-三氯乙醛。在5%氧气浓度下观察到显著的还原脱氯速率，表明这些反应可以在部分有氧条件下发生。这些研究突出了在一系列氧气张力下使用需氧细菌恶臭假单胞菌G786对混合废物进行还原脱卤的潜力，而这些混合废物只能被专性厌氧细菌以极低的速率降解。
