Isoenzyme pattern and immunological properties of arginase in normal and hyperargininemia fibroblasts

Arginase deficiency is an inborn error of the last step in the urea cycle and leads to profound hyperargininemia. The enzyme deficiency has been demonstrated in the liver and red blood cells. In cultured patient fibroblasts, the activity is normal. Arginase exists in multiple molecular forms only one of which is missing in hyperargininemic patients. In fibroblasts, three arginase isoenzymes can be demonstrated by DEAE-cellulose column chromatography, two by electrophoresis and by immunoprecipitation methods. From the present data, it is improbable that part of the A1 isoenzyme in fibroblasts originates from fetal calf serum arginase which supplements the culture media. None of the techniques for the separation and analyses of arginase isoenzyme allows to differentiate between the normal and the arginase-deficient phenotype. A possible explanation would be that the defect in A1 arginase observed in the liver is the result of a regulatory defect.