Measurement of Arginase Activity in Erythrocytes in Newborns and Children and its Correlation with Plasma Ammonia Concentration

ABSTRACT

Arginase is a urea cycle enzyme which catalyzes the cleavage of L-arginine to L-ornithine,and urea. Arginase deficiency is inherited as an autosomal recessive genetic disorder. Hyperammonemia refers to a condition with elevated levels of ammonia in the blood, which is a product of protein degradation. The lack of the arginase enzyme results in excessive accumulation of nitrogen, in the form of ammonia (hyperammonemia) and arginine (hyperargininemia) in the blood. In the present study, the erythrocyte arginase activity is measured along with plasma ammonia concentration in the newborns and children. The study group consists of 133 subjects which are divided into two groups based on the ammonia level. Group 1 consists of subjects with normal ammonia (n=92) and Group 2 consists of subjects with high ammonia (n=41). We found a significant decrease in arginase activity in the high ammonia group compared to the normal ammonia group. A significant negative correlation between arginase and ammonia is observed in both the groups. The result of this study suggests that arginase deficiency could be the cause for hyperammonemia in these cases. Hence, we suggest that estimation of erythrocyte arginase activity can be used as a screening procedure to detect arginase deficiency in newborns, infants, and children with hyperammonemia