The long-term objectives of this research program are the elucidation of the enzymatic mechanisms of steroid transformmtions in animal and microbial systems by the isolation and characterization of the pertinent enzymes, and the application of these basic studies in enzymology and steroid biochemistry to problems of prostatic disease, reproductive function, and inflammation. The immediate specific aims are: (1) To broaden the scope of enzymatic methods for the microestimation of steroids by (a) isolation of novel hydroxysteroid dehydrogenases with more stringent specificities, and (b) simplification of assay procedures through the development of a transhydrogenase assay between NAD and NAD analogs in which steroids act catalytically. (2) Use of these techniques to analyze: (a) Regulation by steroids and gonadotropins of androgen biosynthesis in rat testicular cell cultures by measurement of secreted steroids and steroid-transforming enzymes; and (b) steroid patterns in normal and hyperplastic prostate glands of dogs and men, in the hope of understanding the pathogenesis of the hyperplastic state (BPH) which commonly afflicts man. (3) Elucidation of the properties and functions of the liver 3Alpha-hydroxysteroid dehydrogenase, a major xenobiotic inactivating enzyme, which is also inhibited by steroidal and non-steroidal anti-inflammatory agents. Search for further evidence to show whether this enzyme participates in the mediation of inflammation, by determining its substrate and inhibitor specificities, and its possible role in prostaglandin metabolism. This information may not only shed light on the chemistry of inflammation, but also could provide leads for its control. (4) Description of the detailed molecular structure and catalytic mechanism of the crystalline Delta5-3-ketosteroid isomerase of Pseudomonas testosteroni by NMR, EPR and X-ray diffraction spectroscopy, to delineate the molecular basis for the high specificity and affinity of the steroid-protein binding, and the mechanism of the remarkable catalytic activity of this enzyme. Such information could provide clues to the design of inhibitors of the biosynthesis of steroid hormones, and insight into the fundamental mechanisms of enzyme catalysis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK007422-24
Application #
3224527
Study Section
Biochemical Endocrinology Study Section (BCE)
Project Start
1976-05-01
Project End
1989-07-31
Budget Start
1987-08-01
Budget End
1988-07-31
Support Year
24
Fiscal Year
1987
Total Cost
Indirect Cost
Name
Johns Hopkins University
Department
Type
Schools of Medicine
DUNS #
045911138
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Zhao, Q; Abeygunawardana, C; Mildvan, A S (1997) NMR studies of the secondary structure in solution and the steroid binding site of delta5-3-ketosteroid isomerase in complexes with diamagnetic and paramagnetic steroids. Biochemistry 36:3458-72
Zhao, Q; Abeygunawardana, C; Gittis, A G et al. (1997) Hydrogen bonding at the active site of delta 5-3-ketosteroid isomerase. Biochemistry 36:14616-26
Zhao, Q; Abeygunawardana, C; Mildvan, A S (1996) 13C NMR relaxation studies of backbone and side chain motion of the catalytic tyrosine residue in free and steroid-bound delta 5-3-ketosteroid isomerase. Biochemistry 35:1525-32
Zhao, Q; Abeygunawardana, C; Talalay, P et al. (1996) NMR evidence for the participation of a low-barrier hydrogen bond in the mechanism of delta 5-3-ketosteroid isomerase. Proc Natl Acad Sci U S A 93:8220-4
Zhao, Q; Mildvan, A S; Talalay, P (1995) Enzymatic and nonenzymatic polarizations of alpha,beta-unsaturated ketosteroids and phenolic steroids. Implications for the roles of hydrogen bonding in the catalytic mechanism of delta 5-3-ketosteroid isomerase. Biochemistry 34:426-34
Zhao, Q; Li, Y K; Mildvan, A S et al. (1995) Ultraviolet spectroscopic evidence for decreased motion of the active site tyrosine residue of delta 5-3-ketosteroid isomerase by steroid binding. Biochemistry 34:6562-72
Austin, J C; Zhao, Q; Jordan, T et al. (1995) Ultraviolet resonance Raman spectroscopy of delta 5-3-ketosteroid isomerase revisited: substrate polarization by active-site residues. Biochemistry 34:4441-7
Wu, P; Li, Y K; Talalay, P et al. (1994) Characterization of the three tyrosine residues of delta 5-3-ketosteroid isomerase by time-resolved fluorescence and circular dichroism. Biochemistry 33:7415-22
Li, Y K; Kuliopulos, A; Mildvan, A S et al. (1993) Environments and mechanistic roles of the tyrosine residues of delta 5-3-ketosteroid isomerase. Biochemistry 32:1816-24
Austin, J C; Kuliopulos, A; Mildvan, A S et al. (1992) Substrate polarization by residues in delta 5-3-ketosteroid isomerase probed by site-directed mutagenesis and UV resonance Raman spectroscopy. Protein Sci 1:259-70

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