Mammalian folylpoly-. gamma. -glutamate synthetase. 3. Specificity for folate analogues

Journal Article · Tue Jan 27 04:00:00 EST 1987 · Biochemistry; (United States)

OSTI ID:6620088

George, S; Cichowicz, D J; Shane, B

A variety of folate analogues were synthesized to explore the specificity of the folate binding site of hog liver folypolyglutamate synthetase and the requirements for catalysis. Modifications of the internal and terminal glutamate moieties of folate cause large drops in on rates and/or affinity for the protein. The only exceptions are glutamine, homocysteate, and ornithine analogues, indicating a less stringent specificity around the delta-carbon of glutamate. It is proposed that initial folate binding to the enzyme involves low-affinity interactions at a pterin and a glutamate site and that the first glutamate bound is the internal residue adjacent to the benzoyl group. Processive movement of the polyglutamate chain through the glutamate site and a possible conformational change in the protein when the terminal residue is bound would result in tight binding and would position the ..gamma..-carboxyl of the terminal glutamate in the correct position for catalysis. The 4-amino substitution of folate increases the on rate for monoglutamate derivatives but severely impairs catalysis with diglutamate derivatives. Pteroylornithine derivatives are the first potent and specific inhibitors of folylpolyglutamate synthetase to be identified and may act as analogues of reaction intermediates. Other folate derivatives with tetrahedral chemistry replacing the peptide bond, such as pteroyl-..gamma..-glutamyl-(psi,CH/sub 2/-NH)-glutamate, retain affinity for the protein but are considerably less effective inhibitors than the ornithine derivatives. Enzyme activity was assayed using (/sup 14/C)glutamate.

• Research Organization: Johns Hopkins Univ., Baltimore, MD
• OSTI ID: 6620088
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:2; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
ANIMALS
AROMATICS
AZAARENES
BIOCHEMISTRY
BODY
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
CHEMISTRY
CONFIGURATION INTERACTION
DIGESTIVE SYSTEM
DOMESTIC ANIMALS
DRUGS
ENZYME ACTIVITY
ENZYME INHIBITORS
ENZYMES
FOLIC ACID
GLANDS
GLUTAMIC ACID
HEMATINICS
HEMATOLOGIC AGENTS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LIGASES
LIVER
MAMMALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PTERIDINES
SWINE
TRACER TECHNIQUES
VERTEBRATES
VITAMIN B GROUP
VITAMINS