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Time dependent model for hemoglobin and allosteric enzymes. II.
Author(s) -
Bush Robert Ter,
Thompson Colin J.
Publication year - 1971
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360100807
Subject(s) - chemistry , tetramer , hemoglobin , carbon monoxide , allosteric regulation , kinetics , ligand (biochemistry) , hemoglobin a , stereochemistry , thermodynamics , enzyme , biochemistry , catalysis , receptor , physics , quantum mechanics
The time‐dependent theory developed in Part I is specialized to treat tetrameric hemoglobin, and the results of the theory for dimeric‐and tetrameric hemoglobin are compared with data on the kinetics of the reactions of hemoglobin with carbon monoxide and oxygen at various salt concentrations for the case of large concentration of ligand relative to that of hemoglobin. The fit of the theoretical results to the data suggests that hemoglobin at a 2 M salt concentration is predominantly dimeric and that the tetramer should be taken as the functional unit to explain the kinetics of the reactions of normal hemoglobin. A relationship is established between the time‐dependent theory arid Adair's Intermediate Compound Hypothesis (I.C.H.) for hemoglobin, as brought to its present state by Gibson and Roughton. A generalization (G.I.C.H.) of the I.C.H. is presented and is shown to be equivalent to the time‐dependent theory in the limit of infinite ligand concentration. The I.C.H. is shown to be an excellent approximation to the centralized theory (G.I.C.H.) in this limit.