Inactivation of dopamine. beta. -hydroxylase by. beta. -ethynyltyramine: Kinetic characterization and covalent modification of an active site peptide

Journal Article · Tue May 02 04:00:00 EDT 1989 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00435a032· OSTI ID:5353803

DeWolf, Jr, W E; Chambers, P A; Southan, C; Saunders, D; Kruse, L I ^[1]

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1. Smith Kline French Laboratories, King of Prussia, PA (USA)

{beta}-Ethynyltyramine has been shown to be a potent, mechanism-based inhibitor of dopamine {beta}-hydroxylase (DBH). This is evidenced by pseudo-first-order, time-dependent inactivation of enzyme, a dependence of inactivation on the presence of ascorbate and oxygen cosubstrates, the ability of tyramine (substrate) and 1-(3,5-difluoro-4-hydroxybenzyl)imidazole-2-thione (competitive multisubstrate inhibitor) to protect against inactivation, and a high affinity of {beta}-ethynyltyramine for enzyme. Inactivation of DBH by {beta}-ethynyltyramine is accompanied by stoichiometric, covalent modification of the enzyme. Analysis of the tryptic map following inactivation by ({sup 3}H)-{beta}-ethynyltyramine reveals that the radiolabel is associated with a single, 25 amino acid peptide. The sequence of the modified peptide is given. In studies using the separated enantiomers of {beta}-ethynyltyramine, the authors have found the R enantiomer to be a reversible, competitive inhibitor versus tyramine substrate. The S enantiomer, while also being a competitive inhibitor, is hydroxylated by DBH to give the expected {beta}-ethynyloctopamine product and also efficiently inactivates the enzyme. The partition ratio for this process is very low and has been estimated to be about 2.5.

• OSTI ID: 5353803
• Journal Information: Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 28:9; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINES
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOCHEMICAL REACTION KINETICS
BIOCHEMISTRY
BIOLOGICAL EFFECTS
CARDIOTONICS
CARDIOVASCULAR AGENTS
CHEMISTRY
DOPAMINE
DRUGS
ENZYMES
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
HYDROXYLASES
INACTIVATION
ISOENZYMES
KINETICS
NEUROREGULATORS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PHENOLS
POLYPHENOLS
REACTION KINETICS
STEREOCHEMISTRY
SYMPATHOMIMETICS
TRITIUM COMPOUNDS
TYRAMINE