Interpretation of the effect of an oscillating electric field on membrane enzymes.
Theoretical expressions for the frequency and amplitude dependence of the rate of a catalyzed reaction are fitted to the data of Graziana et al. (1990) [Graziana, A., Ranjeva, R., & Teissié, J. (1990) Biochemistry 29, 8313-8318] for Ca2+ uptake by carrot protoplasts in an oscillating electric field. This uptake is a direct (linear) measure of the rate of increase of ATP caused by a plasma membrane enzyme in the oscillating field. The fit gives 20 ms and 33 microseconds for the relaxation times of the enzyme and roughly 3 for the effective number of elementary changes displaced across the membrane by a conformational change of the enzyme in its catalytic cycle. Additional experiments are suggested to define further the mechanism of the enzymatic reaction.
Robertson
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B
Biotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899.
Astumian
R D
RD
D000255:Adenosine Triphosphate / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002384:Catalysis; D002462:Cell Membrane / Q000201:enzymology*; D004574:Electromagnetic Fields; D007700:Kinetics; D008958:Models, Molecular; D010944:Plants / Q000201:enzymology; D011487:Protein Conformation; D011523:Protoplasts / Q000201:enzymology
D000255:Adenosine Triphosphate; D002118:Calcium