Isotopic and stereochemical probes of the mechanism of bovine plasma amine oxidase

Thesis/Dissertation · Tue Dec 31 23:00:00 EST 1985

OSTI ID:6974617

Farnum, M F

Isotopic and stereochemical probes have been employed to investigate the mechanisms of bovine plasma amine oxidase (BPAO). The pH dependence of isotope effects on steady-state parameters for benzylamine oxidation indicate that the C-H bond breaking step is fully rate-limiting on k/sub cat//K/sub m/ over the experimental pH range. The rate of enzyme reoxidation appears to be partially rate-limiting on k/sub cat/ as values of /sup D/k/sub cat/ are reduced relative to /sup D/k/sub cat//K/sub m/ from pH 5.5 - 10.0. Two microscopic ionizations on k/sub cat//K/sub m/, pK/sub 1/ = 8.0 +/- 0.10 and pK/sub s/ = 9.0 +/- 0.16, are ascribed to an active site residue which must be unprotonated for catalysis, and to substrate binding in the unionized form to the enzyme, respectively. EF/sub 1/ undergoes a pK/sub a/ perturbation from 8.0 to 5.6 in the E x S complex as a result of charge from the protonated imine nitrogen of the enzyme substrate Schiff's base. A pK/sub a/ of 5.5 +/- 0.1 is observed in the pH profile for exchange of tritium from C-2 during oxidation of (2-/sup 3/H)-dopamine. These data support the conclusion that EB/sub 1/ catalyzes both imine exchange at C-2 of phenethylamine substrates as well as substrate oxidation at C-1.

• Research Organization: California Univ., Berkeley (USA)
• OSTI ID: 6974617
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINE OXIDASES
AMINES
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
CARDIOTONICS
CARDIOVASCULAR AGENTS
CATTLE
DOMESTIC ANIMALS
DOPAMINE
DRUGS
ENZYMES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPE EFFECTS
LABELLED COMPOUNDS
MAMMALS
NEUROREGULATORS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PHENOLS
POLYPHENOLS
RUMINANTS
STEREOCHEMISTRY
SYMPATHOMIMETICS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES