The Anoxic Metabolism of Estrogens by the Denitrifying Bacteria

The microbial degradation of steroids is challenging because of its complex chemical structure and low solubility in water. The intermediates involved in oxic cholesterol or testosterone degradation have been studied in some detail. According to these results some microorganisms and microbial enzymes have been applied in pharmaceutical industry. The oxic steroid catabolism includes some oxygenase-catalyzed reactions which require molecular oxygen as a co-substrate. However, little is known about the mechanisms that operate in anoxic steroid metabolism. It is clear that anoxic metabolism involves unprecedented, oxygen-independent reactions. In my previous work, the initial steps involved in the anoxic cholesterol or testosterone degradation have been proposed, and corresponding genes and enzymes have also been characterized. These results have been published in some famous scientific journals of microbiology and biochemistry. Interestingly, nothing is known about the mechanisms operate in oxic or anoxic catabolism of estrogens by bacteria. Recently, a novel bacterial strain, Steroidobacter denitrificans, that has the ability to degrade estrogens (e. g. estrone and estradiol) aerobically and anaerobically has been isolated and characterized. In this study we will utilize S. denitrificans as the model organism. To understand how estrogens are metabolized by S. denitrificans, the chemical, molecular biological, and biochemical approaches will be applied. The specific aims are: (1) to isolate and identify the intermediates involved in oxic and anoxic estrogen-metabolizing pathway; (2) to sequence the genomic DNA of S. denitrificans, and then to search for the corresponding genes; (3) to purify and characterize the enzymes that catalyzes the biotransformation of estrogens. Consider that (1) some steroids are used as drugs, and most steroids are produced industrially by the process of biotransformation; (2) The estrogens belonging to endocrine disrupting agents have also resulted in physiological impacts to wildlife in environment, the study on microbial steroid metabolism of estrogens may unravel novel enzymes and biotransformation processes, and its potential impact on biotechnological, pharmaceutical, and clinical applications can be expected.

Project ID:PA10101-1609
External Project ID:NSC100-2311-B001-032-MY3