REACTION OF OZONE WITH ENZYMES OF ERYTHROCYTE-MEMBRANES

Ozone is a widespread component of polluted air. It is the cause of ma ny adverse effects on the lung such as decreased athletic performance and exacerbation of asthma. Ozone inactivated acetylcholine esterase ( AChE) both in intact washed human erythrocytes and in ghosts prepared from the erythrocytes. This is consistent (a) with the location of ACh E on the outer face of the membrane and (b) with the change in structu re of AChE when amino acids were oxidized. The glyceraldehyde-3-phosph ate dehydrogenase (G3PDH) of intact washed erythrocytes was unaffected by ozone. However, ozone severely inactivated G3PDH of ghosts, much m ore severely than AChE in ghosts. This result raised questions about t he relative permeability of intact erythrocytes and ghosts and also ab out the inherent susceptibility of the two enzymes. Inhibition of the ozone-treated erythrocyte AChE with the competitive inhibitor trimethy l-(p-aminophenyl) ammonium chloride was measured. The inhibited enzyme had a higher K-M and slightly lower V-max than the control. Ozone did not affect the K-M of the uninhibited enzyme but decreased the K-M of the inhibited enzyme. Ozone decreased the V-max of both the inhibited and the uninhibited enzyme. The K-I was unchanged by the treatment wi th ozone. This suggested that the active site of the enzyme was not af fected by ozone, but other features of the protein were changed by ozo ne. The effects of products of lipid ozonolysis [hydrogen peroxide, no nanal, and oyl-2-(9-oxononanyl)-sn-3-glycerophosphorylcholine (PN1PC)] were tested on the ghost preparations. The ozonolysis products were t ested at concentrations equivalent to calculated amounts that could ha ve been produced by ozone. Hydrogen peroxide had no effect on the G3PD H and AChE. Nonanal slightly increased the permeability of the ghost m embrane, as judged by the increase in rate of G3PDH in the absence of Triton X-100, but did not inhibit enzyme activity. PN1PC increased the permeability of the ghosts, as judged by the increase in rate of G3PD H in the absence of Triton X-100. There was also an increase in the ac tivity of G3PDH in the presence of Triton X-100, AChE was not inhibite d by ozone in the presence or absence of Triton X-100. (C) 1996 Academ ic Press, Inc.