Biomaterial Database

Affinity labelling of liver alcohol dehydrogenase. Effects of pH and buffers on affinity labelling with iodoacetic acid and (R, S)-2-bromo-3-(5-imidazolyl)propionic acid. 1981

C Syvertsen, and J S McKinley-McKee

Both iodoacetic acid and (R,S)-2-bromo-3-(5-imidazolyl)propionic acid (BrImPpOH) react with liver alcohol dehydrogenase in an affinity labelling mechanism between pH 6.1 and 10.5. The buffer-independent dissociation constants and the first-order rate constants have been determined as a function of pH. With BrImPpOH a pKa close to 9 for the free enzyme is assigned to the zinc-water ionization. The buffers used exerted a protective effect upon the inactivation of the enzyme by iodoacetic acid and BrImPpOH. Phosphate buffer showed a high degree of protection especially at lower pH, while zwitterionic buffers like Mes (4-morpholineethanesulfonic acid), Pipes (1,4-piperazinediethanesulfonic acid), Epps [4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid] and Bicine [N,N-bis(2-hydroxyethyl)glycine] gave less protection to various degrees. An exception was Ches (cyclohexylaminoethanesulfonic acid) which had an anomalously high affinity for the iodoacetate binding site. The dissociation constants of the buffers were calculated for the case of inactivation by both iodoacetic acid and BrImPpOH.

UI	MeSH Term	Description	Entries
D007093	Imidazoles	Compounds containing 1,3-diazole, a five membered aromatic ring containing two nitrogen atoms separated by one of the carbons. Chemically reduced ones include IMIDAZOLINES and IMIDAZOLIDINES. Distinguish from 1,2-diazole (PYRAZOLES).
D007461	Iodoacetates	Iodinated derivatives of acetic acid. Iodoacetates are commonly used as alkylating sulfhydryl reagents and enzyme inhibitors in biochemical research.	Iodoacetic Acids,Acids, Iodoacetic
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
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D002021	Buffers	A chemical system that functions to control the levels of specific ions in solution. When the level of hydrogen ion in solution is controlled the system is called a pH buffer.	Buffer
D006736	Horses	Large, hoofed mammals of the family EQUIDAE. Horses are active day and night with most of the day spent seeking and consuming food. Feeding peaks occur in the early morning and late afternoon, and there are several daily periods of rest.	Equus caballus,Equus przewalskii,Horse, Domestic,Domestic Horse,Domestic Horses,Horse,Horses, Domestic
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
D000345	Affinity Labels	Analogs of those substrates or compounds which bind naturally at the active sites of proteins, enzymes, antibodies, steroids, or physiological receptors. These analogs form a stable covalent bond at the binding site, thereby acting as inhibitors of the proteins or steroids.	Affinity Labeling Reagents,Labeling Reagents, Affinity,Labels, Affinity,Reagents, Affinity Labeling
D000426	Alcohol Dehydrogenase	A zinc-containing enzyme which oxidizes primary and secondary alcohols or hemiacetals in the presence of NAD. In alcoholic fermentation, it catalyzes the final step of reducing an aldehyde to an alcohol in the presence of NADH and hydrogen.	Alcohol Dehydrogenase (NAD+),Alcohol Dehydrogenase I,Alcohol Dehydrogenase II,Alcohol-NAD+ Oxidoreductase,Yeast Alcohol Dehydrogenase,Alcohol Dehydrogenase, Yeast,Alcohol NAD+ Oxidoreductase,Dehydrogenase, Alcohol,Dehydrogenase, Yeast Alcohol,Oxidoreductase, Alcohol-NAD+