Comparison of angiotensin converting enzyme activity in Antarctic teleosts: Trematomus bernacchii and Chionodraco hamatus.

Aim: The aim of our research was to characterize some biochemical parameters of angiotensin converting enzyme (ACE) in the icefish Chionodraco hamatus and the red-blooded Trematomus bernacchii and to compare ACE activity in tissues of the two species of Antarctic teleosts. Methods: ACE activity was determined by incubating crude tissue homogenates in presence of N-[3-(2-furyl)acryloyl]L-phenylalanyl-glycyl-glycine (FAPGG), a synthetic substrate of somatic and testicular ACE. Substrate and product (FAP) were separated by reverse phase HPLC analysis. To compare the ACE activity of two Antarctic teleosts, biochemical parameters such as the optimum pH’s, temperatures, and chloride concentrations for ACE activity were determined, and the activity of the ACE inhibitors captopril and lisinopril was studied. Results: The characterization of ACE activities in two fishes was performed using gill homogenates. The optimum pH ranges were 8.5 at 25°C and optimum chloride concentrations were about 300 mM. I50 values for captopril and lisinopril were similar in two fishes. The optimum temperature was 50°C for T. bernachii and 35°C for C. hamatus. Conclusion: The data show similar ACE activity in the two Antarctic teleosts. The only significant difference regarded the optimum temperature for ACE activity, lower for C. hamatus than for T. bernacchii, probably due to the enzyme’s adaptation to the constantly cold temperatures of animal’s environment.