Effect of low frequency, low amplitude magnetic fields on the permeability of cationic liposomes entrapping carbonic anhydrase: II. No evidence for surface enzyme involvement med./bio.

Previous observations (see publication 3933) indicate that combined 7 Hz sinusoidal and parallel static magnetic fields can induce a significant increase in diffusion rate of substrate across carbonic anhydrase-loaded liposomes. A direct involvement of charges of stearylamine on the lipid membrane surface was also found.
In this study the influence of 7 Hz magnetic fields (B_dc=50 µT and B_acpeak=50 µT) on the kinetic of carbonic anhydrase located on the external surface of liposomes was examined. Specifically, it was evaluated whether conformational changes in the catalytic and/or substrate-binding sites of the enzyme might cause the observed effect on carbonic anhydrase-loaded liposomes.

• organelle/cell part
• loaded and empty liposomes

No difference in the apparent K_m (Michaelis-Menten constant) between exposed and sham-exposed samples was revealed. On the contrary the apparent V_max (maximal velocity of an enzyme-catalyzed reaction) was increased by approximately a factor of 2 after exposure. In spite of the proteolytic digestion (proteinase K incubation) of this external carbonic anhydrase, a significant increase of enzymatic activity, as a function of increase in the diffusion rate of substrate across the lipid bilayer, was found in the exposed samples.
Based on these data, a conformational change induced by the field on the carbonic anhydrase located on the external surface of liposomes is excluded as an explanation for previous observations, supporting the primary role of bilayer stearlyamine in the interaction with ELF.
A model of extremely low frequency interaction explaining the physical phenomenon induced on the dipole of stearylamine has been developed.