Effects of anesthetics and dichlorodifluoromethane on the activities of glyceraldehyde-phosphate dehydrogenase and pectin methylesterase

Abstract

Solutions of glucose-3-phosphate dehydrogenase (GPD) and pectin methylesterase (PME) were exposed to various anesthetics and dichlorodifluoromethane (F-12) to determine the abilities of these chemicals to inhibit enzyme activity. An aqeuous solution of PME was exposed to saturation levels of the test chemicals for 30 min at 21°. All test chemicals were inhibitory (measured after release of the test chemical) with propane being most inhibitory followed in order by F-12, cyclopropane, Ethrane (F 2HCOF 2CCHClF) and halothane (CF 3CHClBr). GPD was exposed to various concentrations of F-12 and halothane for various times at 0° and 33°. Halothane at 33° and a saturation concentration reduced the initial reaction velocity of GPD to zero after a 10-min exposure period. F-12 was somewhat less inhibitory than halothane, but inhibition in all instances was irreversible. Halothane was found to affect the circular dichroism and optical rotary dispersion spectra of GPD, with the magnitude of the changes generally increasing with treatment time. The observed changes were believed to arise from side-chain transitions of GPD.