The pathways of mammalian cysteine metabolism are numerous and complex. At least 12 distinct enzymes active toward cysteine have been identified, and the pathways initiated by these enzymes have been shown to lead to a multitude of intermediate products. Many of the pathways eventually intersect to either regenerate cysteine or to form a small number of catabolic products (taurine, sulfate, pyruvate). The multiplicity and complexity of these pathways have impeded attempts to determine the role of individual pathways in the overall metabolism of cysteine. The accurate interpretation of in vivo pulse-labeling studies is seriously hindered, for example, by cysteine recycling and pathway convergence. Further studies would be greatly facilitated by techniques which allow selected pathways to be specifically inhibited in vivo and by the development of cysteine analogs which are metabolized by only a small number of the existing pathways. By reducing the number of metabolic pathways available, these techniques would substantially simplify the interpretation of in vivo experiments. Selective enzyme inhibitors should also be of use in the manipulation of cysteine metabolism for therapeutic purposes; applications are indicated in the chemotherapy of trypanosomiasis, in the sensitization of tumor cells to killing leukocytes, radiation and chemical agents, and in the inhibition of leukotriene C and prostaglandin E2 synthesis. The elucidation of mammalian cysteine metabolism through the design, synthesis and in vivo utilization of modified substrates and enzyme specific inhibitors is the principal objective of the investigations proposed. Although prospective inhibitors and substrate analogs will be tested with isolated enzymes, the investigations will center on studies with intact mice and rats and, to a lesser extent, the perfused rat kidney. The studies will focus initially on three specific areas of cysteine metabolism (i) the pathways of taurine biosynthesis, (ii) the mechanism of extracellular thiol oxidation, and (iii) the control of glutathione turnover. Subsequent studies will define the quantitative importance of taurine biosynthesis relative to the other reactions of cysteine catabolism and will examine factors controlling cysteine homeostasis in the whole animal.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis, Diabetes, Digestive and Kidney Diseases (NIADDK)
Type
Research Project (R01)
Project #
5R01AM026912-06
Application #
3151684
Study Section
Biochemistry Study Section (BIO)
Project Start
1980-04-01
Project End
1988-03-31
Budget Start
1985-04-01
Budget End
1986-03-31
Support Year
6
Fiscal Year
1985
Total Cost
Indirect Cost
Name
Weill Medical College of Cornell University
Department
Type
Schools of Medicine
DUNS #
201373169
City
New York
State
NY
Country
United States
Zip Code
10065
Lippitz, B E; Halperin, E C; Griffith, O W et al. (1990) L-buthionine-sulfoximine-mediated radiosensitization in experimental interstitial radiotherapy of intracerebral D-54 MG glioma xenografts in athymic mice. Neurosurgery 26:255-60
Friedman, H S; Colvin, O M; Griffith, O W et al. (1989) Increased melphalan activity in intracranial human medulloblastoma and glioma xenografts following buthionine sulfoximine-mediated glutathione depletion. J Natl Cancer Inst 81:524-7
Weinstein, C L; Griffith, O W (1988) Cysteinesulfonate and beta-sulfopyruvate metabolism. Partitioning between decarboxylation, transamination, and reduction pathways. J Biol Chem 263:3735-43
Griffith, O W (1987) Mammalian sulfur amino acid metabolism: an overview. Methods Enzymol 143:366-76
Hayward, M A; Campbell, E B; Griffith, O W (1987) Sulfonic acids: L-homocysteinesulfonic acid. Methods Enzymol 143:279-81
Griffith, O W (1987) Amino acid sulfoximines: alpha-ethylmethionine sulfoximine. Methods Enzymol 143:286-91
Weinstein, C L; Griffith, O W (1987) Multiple forms of rat liver cysteinesulfinate decarboxylase. J Biol Chem 262:7254-63
Griffith, O W; Weinstein, C L (1987) beta-Sulfopyruvate. Methods Enzymol 143:221-3
Griffith, O W (1987) Amino acid sulfones: S-benzyl-DL-alpha-methylcysteine sulfone. Methods Enzymol 143:274-9
Griffith, O W; Weinstein, C L (1987) Sulfinic acids from disulfides: L-[35S]cysteinesulfinic acid. Methods Enzymol 143:270-4

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