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
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
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ACID PHOSPHATASE
CHEMICAL COMPOSITION
CHOLINESTERASE
ENZYME ACTIVITY
CYSTEINE
BIOLOGICAL FUNCTIONS
HISTIDINE
ACETATES
CARBON 13
CATTLE
FRACTIONATION
HYDROLYSIS
LIVER
MOLECULAR WEIGHT
OXYGEN 18
PH VALUE
TRACER TECHNIQUES
WATER
AMINO ACIDS
ANIMALS
AZOLES
BODY
CARBON ISOTOPES
CARBOXYLESTERASES
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DECOMPOSITION
DIGESTIVE SYSTEM
DOMESTIC ANIMALS
ENZYMES
ESTERASES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FUNCTIONS
GLANDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROLASES
IMIDAZOLES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
LYSIS
MAMMALS
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PHOSPHATASES
RUMINANTS
SEPARATION PROCESSES
SOLVOLYSIS
STABLE ISOTOPES
THIOLS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques