Biomaterial Database

pH dependence of deuterium isotope effects and tritium exchange in the bovine plasma amine oxidase reaction: a role for single-base catalysis in amine oxidation and imine exchange. 1986

M Farnum, and M Palcic, and J P Klinman

The pH dependence of steady-state parameters for [1,1-1H2]- and [1,1-2H2]benzylamine oxidation and of tritium exchange from [2-3H]dopamine has been measured in the bovine plasma amine oxidase reaction. Deuterium isotope effects on kcat/Km for benzylamine are observed to be constant, near the intrinsic value of 13.5, over the experimental pH range, indicating that C-H bond cleavage is fully rate limiting for this parameter. As a consequence, pKa values derived from kcat/Km profiles, 8.0 +/- 0.1 (pK1) and 9.0 +/- 0.16 (pKs), can be ascribed to microscopic pKa values for the ionization of an essential active site residue (EB1) and substrate, respectively. Profiles for kcat and Dkcat show that EB1 undergoes a perturbation from 8.0 to 5.6 +/- 0.3 (pK1') in the presence of substrate; additionally, a second ionization, pK2 = 7.25 +/- 0.25, is observed to mediate but not be essential for enzyme reoxidation. The pH dependence of the ratio of tritium exchange to product formation for dopamine also indicates base catalysis with a pKexch = 5.5 +/- 0.01, which is within experimental error of pK1'. We conclude that the data presented herein support a single residue catalyzing both substrate oxidation and exchange, consistent with recent stereochemical results that implicate a syn relationship between these processes [Farnum, M., & Klinman, J.P. (1985) Fed. Proc., Fed. Am. Soc. Exp. Biol. 44, 1055]. This conclusion contrasts with earlier kinetic data in support of a large rate differential for the exchange of hydrogen from C-1 vs. C-2 of phenethylamine derivatives [Palcic, M.M., & Klinman, J.P. (1983) Biochemistry 22, 5957-5966].(ABSTRACT TRUNCATED AT 250 WORDS)

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D011865	Radioisotope Dilution Technique	Method for assessing flow through a system by injection of a known quantity of radionuclide into the system and monitoring its concentration over time at a specific point in the system. (From Dorland, 28th ed)	Radioisotope Dilution Technic,Dilution Technic, Radioisotope,Dilution Technics, Radioisotope,Dilution Technique, Radioisotope,Dilution Techniques, Radioisotope,Radioisotope Dilution Technics,Radioisotope Dilution Techniques,Technic, Radioisotope Dilution,Technics, Radioisotope Dilution,Technique, Radioisotope Dilution,Techniques, Radioisotope Dilution
D002417	Cattle	Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.	Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D003903	Deuterium	The stable isotope of hydrogen. It has one neutron and one proton in the nucleus.	Deuterons,Hydrogen-2,Hydrogen 2
D006631	Amine Oxidase (Copper-Containing)	A group of enzymes including those oxidizing primary monoamines, diamines, and histamine. They are copper proteins, and, as their action depends on a carbonyl group, they are sensitive to inhibition by semicarbazide.	Diamine Oxidase,Histaminase,Amine Oxidase, Copper-Containing,Copper Amine Oxidase,Diaminobenzidine Oxidase,Semicarbazide-Sensitive Amine Oxidase,Xylylene Diamine Oxidase,Amine Oxidase, Copper,Amine Oxidase, Copper Containing,Amine Oxidase, Semicarbazide-Sensitive,Copper-Containing Amine Oxidase,Diamine Oxidase, Xylylene,Oxidase, Copper Amine,Oxidase, Copper-Containing Amine,Oxidase, Diamine,Oxidase, Diaminobenzidine,Oxidase, Semicarbazide-Sensitive Amine,Oxidase, Xylylene Diamine,Semicarbazide Sensitive Amine Oxidase
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D000587	Oxidoreductases Acting on CH-NH Group Donors	Enzymes catalyzing the dehydrogenation of secondary amines, introducing a C	Secondary Amine Oxidoreductases,Amine Oxidoreductases, Secondary Amine,Amine Oxidoreductases, Secondary,Oxidoreductases Acting on CH NH Group Donors,Oxidoreductases, Secondary Amine
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