Heat lability studies of glutathione peroxidase and glutathione reductase activities were conducted on rabbit, sheep, rat, human, galago, cat and rhesus monkey lens supernatants. These species represent five mammalian orders. Incubation periods were 10.0 minutes in duration, with temperatures ranging from 25-100° C (depending on which enzyme was being investigated). Results obtained for glutathione peroxidase activity demonstrated nearly identical heat lability profiles for human and rhesus monkey lenses. Both species were extremely labile to heat, losing activity at 30° C and becoming totally inactive at temperatures of 50° C (rhesus monkey) and 55° C (human). Their profiles were very dissimilar to those of the other five species investigated, providing evidence for the existence of an evolutionary break. Glutathione reductase activity was extremely stable under conditions of highly elevated temperature for all seven species investigated. The human lens enzyme, the most stable of the species, maintained nearly 100% of its original activity up to 65° C. Lenticular glutathione reductase activity did not reach zero levels in any of the seven species until a temperature of at least 80° C was attained.
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ACKNOWLEDGMENTS The authors wish to thank the personnel at the following institutions for supplying eye tissue: Duke University Primate Research Center, Oregon Regional Primate Research Center, University of Minnesota Lions Eye Bank and the Veterinary Diagnostic Laboratories at the University of Minnesota. This research was supported in part by the National Institutes of Health research grant EY-01197 and an unrestricted grant from Research to Prevent Blindness (RPB).