Biomaterial Database

Rat liver gamma-butyrobetaine hydroxylase catalyzed reaction: influence of potassium, substrates, and substrate analogues on hydroxylation and decarboxylation. 1988

R S Wehbie, and N S Punekar, and H A Lardy

Institute for Enzyme Research, University of Wisconsin, Madison 53705.

Interaction of rat liver gamma-butyrobetaine hydroxylase (EC 1.14.11.1) with various ligands was studied by following the decarboxylation of alpha-ketoglutarate, formation of L-carnitine, or both. Potassium ion stimulates rat liver gamma-butyrobetaine hydroxylase catalyzed L-carnitine synthesis and alpha-ketoglutarate decarboxylation by 630% and 240%, respectively, and optimizes the coupling efficiency of these two activities. Affinities for alpha-ketoglutarate and gamma-butyrobetaine are increased in the presence of potassium. gamma-Butyrobetaine hydroxylase catalyzed decarboxylation of alpha-ketoglutarate was dependent on the presence of gamma-butyrobetaine, L-carnitine, or D-carnitine in the reaction and exhibited Km(app) values of 29, 52, and 470 microM, respectively. gamma-Butyrobetaine saturation of the enzyme indicated a substrate inhibition pattern in both the assays. Omission of potassium decreased the apparent maximum velocity of decarboxylation supported by all three compounds by a similar percent. beta-Bromo-alpha-ketoglutarate supported gamma-butyrobetaine hydroxylation, although less effectively than alpha-ketoglutarate. The rat liver enzyme was rapidly inactivated by 1 mM beta-bromo-alpha-ketoglutarate at pH 7.0. This inactivation reaction did not show a rate saturation with increasing concentrations of beta-bromo-alpha-ketoglutarate. None of the substrates or cofactors, including alpha-ketoglutarate, protected the enzyme against this inactivation. Unlike beta-bromo-alpha-ketoglutarate, beta-mercapto-alpha-ketoglutarate did not replace alpha-ketoglutarate as a cosubstrate. Both beta-mercapto-alpha-ketoglutarate and beta-glutathione-alpha-ketoglutarate were noncompetitive inhibitors with respect to alpha-ketoglutarate.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008099	Liver	A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.	Livers
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D003653	Decarboxylation	The removal of a carboxyl group, usually in the form of carbon dioxide, from a chemical compound.	Decarboxylations
D006899	Mixed Function Oxygenases	Widely distributed enzymes that carry out oxidation-reduction reactions in which one atom of the oxygen molecule is incorporated into the organic substrate; the other oxygen atom is reduced and combined with hydrogen ions to form water. They are also known as monooxygenases or hydroxylases. These reactions require two substrates as reductants for each of the two oxygen atoms. There are different classes of monooxygenases depending on the type of hydrogen-providing cosubstrate (COENZYMES) required in the mixed-function oxidation.	Hydroxylase,Hydroxylases,Mixed Function Oxidase,Mixed Function Oxygenase,Monooxygenase,Monooxygenases,Mixed Function Oxidases,Function Oxidase, Mixed,Function Oxygenase, Mixed,Oxidase, Mixed Function,Oxidases, Mixed Function,Oxygenase, Mixed Function,Oxygenases, Mixed Function
D006900	Hydroxylation	Placing of a hydroxyl group on a compound in a position where one did not exist before. (Stedman, 26th ed)	Hydroxylations
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001622	Betaine	A naturally occurring compound that has been of interest for its role in osmoregulation. As a drug, betaine hydrochloride has been used as a source of hydrochloric acid in the treatment of hypochlorhydria. Betaine has also been used in the treatment of liver disorders, for hyperkalemia, for homocystinuria, and for gastrointestinal disturbances. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1341)	Lycine,Oxyneurine,Acidin-Pepsin,Betaine Hydrochloride,C.B.B.,Citrate de Bétaïne Beaufour,Citrate de Bétaïne UPSA,Cystadane,Glycine Betaine,Hepastyl,Novobetaine,Scorbo-bétaïne,Stea-16,Acidin Pepsin,AcidinPepsin,Betaine, Glycine,Hydrochloride, Betaine,Scorbo bétaïne,Scorbobétaïne,Stea 16,Stea16
D013379	Substrate Specificity	A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.	Specificities, Substrate,Specificity, Substrate,Substrate Specificities
D050563	gamma-Butyrobetaine Dioxygenase	An enzyme that catalyzes the HYDROXYLATION of gamma-butyrobetaine to L-CARNITINE. It is the last enzyme in the biosynthetic pathway of L-CARNITINE and is dependent on alpha-ketoglutarate; IRON; ASCORBIC ACID; and OXYGEN.	4-Trimethylaminobutyrate, 2-Oxoglutarate Oxygen Oxidoreductase (3-Hydroxylating),Butyrobetaine Hydroxylase,Trimethylaminobutyrate Hydroxylase,gamma-Butyrobetaine Hydroxylase,gamma-Butyrobetaine, 2-Oxoglutarate Dioxygenase,gamma-Butyrobetaine,2-Oxoglutarate Dioxygenase,2-Oxoglutarate Dioxygenase gamma-Butyrobetaine,Dioxygenase gamma-Butyrobetaine, 2-Oxoglutarate,Dioxygenase, gamma-Butyrobetaine,Dioxygenase, gamma-Butyrobetaine,2-Oxoglutarate,Hydroxylase, Butyrobetaine,Hydroxylase, Trimethylaminobutyrate,Hydroxylase, gamma-Butyrobetaine,gamma Butyrobetaine Dioxygenase,gamma Butyrobetaine Hydroxylase,gamma Butyrobetaine, 2 Oxoglutarate Dioxygenase,gamma Butyrobetaine,2 Oxoglutarate Dioxygenase