Biomaterial Database

Enzymatic catalysis in the affinity labelling of liver alcohol dehydrogenase with haloacids. 1981

K H Dahl, and J S McKinley-Mckee

In this work, the inactivation at pH 7.0 of liver alcohol dehydrogenase by iodoacetamide and a series of six haloacids has been studied, and the kinetic constants determined. Enzyme inactivation was compared with the model alkylation of a metal-thiol and a thiolate anion free in solution. The following conclusions resulted. 1. Inactivation of liver alcohol dehydrogenase by iodoacetamide is a direct thiol alkylation, while inactivation by selective alkylation of Cys-46 by the haloacids is facilitated by reversible complex formation. 2. Inactivation half-time for the haloacids ranged over 4-190 min, a difference mainly caused by dissimilar chemical reactivities rather than diverse fitting in the active site. 3. The thiol of Cys-46 is alkylated as a zinc-thiol complex. It is, as such, not especially reactive; indeed it has a nucleophilic reactivity similar to that observed with the model compound free in solution. 4. Affinity labelling of liver alcohol dehydrogenase by haloacids compared with alkylation of the similar group free in solution illustrates enzymatic catalysis by reversible complex formation. With the present series of 'substrates' a rate enhancement of up to 58 000 is seen.

UI	MeSH Term	Description	Entries
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
D011422	Propionates	Derivatives of propionic acid. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the carboxyethane structure.	Propanoate,Propanoic Acid,Propionate,Propanoates,Propanoic Acid Derivatives,Propanoic Acids,Propionic Acid Derivatives,Propionic Acids,Acid, Propanoic,Acids, Propanoic,Acids, Propionic,Derivatives, Propanoic Acid,Derivatives, Propionic Acid
D002384	Catalysis	The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.	Catalyses
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
D000085	Acetates	Derivatives of ACETIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the carboxymethane structure.	Acetate,Acetic Acid Esters,Acetic Acids,Acids, Acetic,Esters, Acetic Acid
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
D000429	Alcohol Oxidoreductases	A subclass of enzymes which includes all dehydrogenases acting on primary and secondary alcohols as well as hemiacetals. They are further classified according to the acceptor which can be NAD+ or NADP+ (subclass 1.1.1), cytochrome (1.1.2), oxygen (1.1.3), quinone (1.1.5), or another acceptor (1.1.99).	Carbonyl Reductase,Ketone Reductase,Carbonyl Reductases,Ketone Reductases,Oxidoreductases, Alcohol,Reductase, Carbonyl,Reductase, Ketone,Reductases, Carbonyl,Reductases, Ketone
D000478	Alkylation	The covalent bonding of an alkyl group to an organic compound. It can occur by a simple addition reaction or by substitution of another functional group.	Alkylations