Two necessary conditions for validation of the hypothesis that changes in the chain length of the naturally occurring poly-Gamma-glutamyl derivatives of the folate co-enzymes play a role in the regulation of one-carbon metabolism are now well established: a) the catalytic efficiency of most folate-dependent enzymes is affected in vitro by the chain length of the folate coenzymes; and b) changes in the chain length distribution of the folates occur in vivo in response to alterations in the steady-state of one-carbon metabolism. It remains to establish how, and in response to which effectors these changes in the folate co-factors occur. Of the two opposing enzyme systems that modify the poly-Gamma-glutamyl chain, the folylpolyglutamate synthetase (FPGS) and the pteroylpolyglutamate hydrolases (the conjugases), the metabolic role or the latter is the least understood. We hypothezise that endo-conjugases, primarily hepatic, are involved in the mobilization of folate stores by degrading in one step the intracellular 5-CH3-H4PteGlun to the circulating 5-CH3-H4Pte-monoglutamate. Exo-conjugases, removing one Glu residue at a time, are believed (together with FPGS) to be involved in the regulation of one-carbon metabolism via midification of the poly-Gamma-glutamyl chain length. To test this hypothesis we propose the following Specific Aims: 1) to continue the development of methods for the study of endo- and exo-conjugases, including specific assays for each of these activities; 2) to study changes in the activity of endo- and exo-conjugases during situations that alter the steady-state of 1-C metabolism; 3) to study the effects of increased folate demand by extrahepatic tissues on endo- and exo-conjugase activities of the liver; and 4) to attempt the purification of endo- and exo-conjugases from rat liver and kidney and study the properties of the purified enzymes with special attention to the study of effectors.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM023453-07
Application #
3271642
Study Section
Biochemistry Study Section (BIO)
Project Start
1978-09-01
Project End
1986-11-30
Budget Start
1984-12-01
Budget End
1985-11-30
Support Year
7
Fiscal Year
1985
Total Cost
Indirect Cost
Name
University of Alabama Birmingham
Department
Type
Sch Allied Health Professions
DUNS #
004514360
City
Birmingham
State
AL
Country
United States
Zip Code
35294