pH dependence of the acetylcholinesterase-catalyzed oxygen exchange between acetate and water/purification and characterization of the low-molecular-weight acid phosphatase from bovine liver: Clarification of the roles of cysteine and histidine at the active site

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6279637

Dayton, B D

Acetylcholinesterase (AChE) catalyzes ester hydrolysis through nucleophilic attack of an active-site serine on the acyl carbon of the substrate, acetylcholine, leading to the formation of an acylenzyme intermediate, with hydrolysis resulting in the production of choline and acetic acid. The first half of the reverse reaction-AChE-catalyzed attack on acetate-was studied over a wide range in pH. Homogeneous enzyme was obtained after chromatography using the synthetic affinity resin 9-(5-carboxypentylamino)acridine. The pH-dependence of AChE-catalyzed acetylthiocholine hydrolysis and its inhibition by acetate implicated one, or possibly two, active site residues in deacylation with pK/sub a/ values of 6.7 and 5.0. The pH-dependence of the enzyme-catalyzed exchange of oxygen between sodium (1-/sup 13/C, /sup 18/O/sub 2/) acetate and water suggested acetic acid as the preferred substrate for exchange, while rate data supported the role of an induced-fit rate-limiting step involving a virtual transition state in catalysis.

• Research Organization: Purdue Univ., Lafayette, IN (USA)
• OSTI ID: 6279637
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACETATES
ACID PHOSPHATASE
AMINO ACIDS
ANIMALS
AZOLES
BIOLOGICAL FUNCTIONS
BODY
CARBON 13
CARBON ISOTOPES
CARBOXYLESTERASES
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CATTLE
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHOLINESTERASE
CYSTEINE
DECOMPOSITION
DIGESTIVE SYSTEM
DOMESTIC ANIMALS
ENZYME ACTIVITY
ENZYMES
ESTERASES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FRACTIONATION
FUNCTIONS
GLANDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HISTIDINE
HYDROGEN COMPOUNDS
HYDROLASES
HYDROLYSIS
IMIDAZOLES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
LIVER
LYSIS
MAMMALS
MOLECULAR WEIGHT
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PH VALUE
PHOSPHATASES
RUMINANTS
SEPARATION PROCESSES
SOLVOLYSIS
STABLE ISOTOPES
THIOLS
TRACER TECHNIQUES
VERTEBRATES
WATER