Amino acids are central to the many metabolic processes that sustain living cells and organisms. The long-term objectives of this research endeavor are to uncover and elucidate new metabolic reactions on the enzymic level involving 4-hydroxyglutamic acid/2- keto-4-hydroxyglutaric acid and threonine, and also to examine the structure/function interrelationships of key enzymes involved in order to establish structural requirements for catalytic and/or regulatory activity. Specifically, in vitro enzyme studies will be carried out to ascertain how 4-hydroxyglutamic acid is converted to glutamic acid in mammals and also to determine how 2-keto-4-hydroxyglutaric acid is utilized by Acetobacter suboxydans, an organism that lacks the conventional Krebs cycle, to biosynthesize di- and tricarboxylic acids. New metabolic intermediates and enzymes involved will be isolated and characterized. Three enzymes, namely, 2-keto-4- hydroxyglutarate aldolase, L-threonine dehydrogenase, and 2-amino- 3-ketobutyrate which we have succeeded in isolating in pure form and substantial quantities, will be the objects of in-depth structure/function studies. Selective chemical modification of these enzymes will be carried out to determine specific amino acid residues that are required for catalytic activity, peptides containing these residues will be separately isolated and sequenced by HPLC methodologies, and their position in the complete primary structure of the enzyme established. The genes for these enzymes will be cloned, selected amino acid. changes in the structure of the enzymes made by site-directed mutagenesis procedures, and the effects of such changes on their catalytic/regulatory properties determined. The aldolase catalyzes a key reaction in the mammalian metabolism of hydroxyproline, the dehydrogenase in the biosynthesis of Vitamin B12 by microorganisms and the formation of aminoacetone (which is excreted by humans), and the dehydrogenase/ lyase combination initiates a new route for serine biosynthesis. The goal is to understand metabolic and enzymic processes since life is dependent on an organized and balanced system of enzymes and since more and more diseased states have fundamental molecular and/or enzymic facets.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK003718-30
Application #
3224410
Study Section
Physiological Chemistry Study Section (PC)
Project Start
1977-12-01
Project End
1992-11-30
Budget Start
1988-12-01
Budget End
1989-11-30
Support Year
30
Fiscal Year
1989
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Type
Schools of Medicine
DUNS #
791277940
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Marcus, J P; Dekker, E E (1995) Identification of a second active site residue in Escherichia coli L-threonine dehydrogenase: methylation of histidine-90 with methyl p-nitrobenzenesulfonate. Arch Biochem Biophys 316:413-20
Chen, Y W; Dekker, E E; Somerville, R L (1995) Functional analysis of E. coli threonine dehydrogenase by means of mutant isolation and characterization. Biochim Biophys Acta 1253:208-14
Marcus, J P; Dekker, E E (1993) pH-dependent decarboxylation of 2-amino-3-ketobutyrate, the unstable intermediate in the threonine dehydrogenase-initiated pathway for threonine utilization. Biochem Biophys Res Commun 190:1066-72
Marcus, J P; Dekker, E E (1993) Threonine formation via the coupled activity of 2-amino-3-ketobutyrate coenzyme A lyase and threonine dehydrogenase. J Bacteriol 175:6505-11
Marcus, J P; Dekker, E E (1993) Identity and some properties of the L-threonine aldolase activity manifested by pure 2-amino-3-ketobutyrate ligase of Escherichia coli. Biochim Biophys Acta 1164:299-304
Mukherjee, J J; Dekker, E E (1992) Inactivation of Escherichia coli 2-amino-3-ketobutyrate CoA ligase by phenylglyoxal and identification of an active-site arginine peptide. Arch Biochem Biophys 299:147-53
Patil, R V; Dekker, E E (1992) Cloning, nucleotide sequence, overexpression, and inactivation of the Escherichia coli 2-keto-4-hydroxyglutarate aldolase gene. J Bacteriol 174:102-7
Dekker, E E; Kitson, R P (1992) 2-Keto-4-hydroxyglutarate aldolase: purification and characterization of the homogeneous enzyme from bovine kidney. J Biol Chem 267:10507-14
Epperly, B R; Dekker, E E (1991) L-threonine dehydrogenase from Escherichia coli. Identification of an active site cysteine residue and metal ion studies. J Biol Chem 266:6086-92
Mukherjee, J J; Dekker, E E (1990) 2-Amino-3-ketobutyrate CoA ligase of Escherichia coli: stoichiometry of pyridoxal phosphate binding and location of the pyridoxyllysine peptide in the primary structure of the enzyme. Biochim Biophys Acta 1037:24-9

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