Mechanism of adenylate kinase. Is there a relationship between local substrate dynamics, local binding energy, and the catalytic mechanism
- Ohio State Univ., Columbus (USA)
Adenylyl ({beta},{gamma}-methylene)diphosphonic acid (AMPPCP) labeled with deuterium at the adenine ring ((8-{sup 2}H)AMPPCP) and at the {beta},{gamma}-methylene group (AMPPCD{sub 2}P), as well as adenosine 5{prime}-monophosphate labeled at the adenine ring ((8-{sup 2}H)AMP), was synthesized and used for deuterium nuclear magnetic resonance (NMR) determination of effective correlation times ({tau}{sub c}) of the free nucleotide and the complexes with adenylate kinase (AK). Extensive and rigorous control experiments and theoretical analysis were performed to justify the validity of the experimental approaches, particularly the fast exchange condition, and the reliability of the {tau}{sub c} values obtained. For the free nucleotide, the results suggest that the phosphonate group of free AMPPCP possesses appreciable local mobility relative to the adenine ring and that complexation with Mg{sup 2+} greatly reduced such a local mobility. These results suggest that the adenine ring of substrates is rigidly bound in all cases, that the phosphonate chain of AMPPCP possesses considerable local mobility, and that Mg{sup 2+} reduces such local mobility but does not totally immobilize it. The results suggest that no general correlation exists between the local rigidity of portions of a bound substrate and the corresponding (ground state) local binding energy contributed by these portions. The authors have found that the K{sub i} values for the mixture, the {Delta} isomer, and the {Lambda} isomer of CrATP are 16, 11, and 20 {mu}M, respectively, which suggest that ground-state binding by AK is stereochemically permissive. The results of both problems fully support the conclusion that the phosphonate chain of AK-MgAMPPCP possesses considerable local mobility and illuminate the relationship between the dynamics of bound substrates and the catalytic mechanism.
- OSTI ID:
- 6969464
- Journal Information:
- Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 28:23; ISSN 0006-2960; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
62 RADIOLOGY AND NUCLEAR MEDICINE
BIOCHEMICAL REACTION KINETICS
BIOSYNTHESIS
CHEMICAL SHIFT
CHROMATOGRAPHY
DEUTERIUM COMPOUNDS
ENZYMES
ESTERS
HYDROGEN COMPOUNDS
KINETICS
LIGANDS
LIQUID COLUMN CHROMATOGRAPHY
MAGNETIC RESONANCE
MOLECULAR STRUCTURE
NUCLEAR MAGNETIC RESONANCE
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHONIC ACID ESTERS
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHOTRANSFERASES
REACTION KINETICS
RESONANCE
SEPARATION PROCESSES
SUBSTRATES
SYNTHESIS
TRANSFERASES