Biochemical Analysis of Arginase and Ornithine Carbamoyltransferase in Human Vitreous Humor

Background esence of arginase and ornithine carbamoyltransferase (OTCʹase) enzymes in human vitreous humor after death was investigated in this study. To the best of our knowledge, there is no prior report on the activity of arginase or ornithine carbamoyltransferase in human vitreous humor. s esence of arginase and OTCʹase activities were examined in the human vitreous humor of 19 samples. Spectrophotometric methods were used to determine activities of arginase and OTCʹase. s se activity was detected in human vitreous humor, whereas OTCʹase activity was below the detection limit. Therefore, we focused on biochemical analysis of arginase in human vitreous humor. Kinetic properties of arginase activity in vitreous humor were optimized. In contrast to other arginases, optimal preincubation temperature and pH were 40°C and 8.8, respectively. Km of vitreous arginase for L-arginine was 6 mM. Preincubation of the enzyme with Mn2+ ions caused a significant increase (33%) in arginase activity. sions tivity and presence of arginase as well as its kinetics in human vitreous are documented in this study. Biochemical functions and the importance of arginase in vitreous humor are not well understood. However, its presence may be explained by means of its involvement in polyamine biosynthesis as observed in the other extrahepatic tissues.