PROPERTIES OF HUMAN ADULT AND FETAL RED BLOOD CELL ARGINASE: A POSSIBLE DIAGNOSTIC TEST FOR ARGINASE DEFICIENCY

Abstract

Hyperargininemia due to arginase deficiency results in a syndrome of progressive neurological and intellectual deterioration and is inherited in an autosomal recessive manner. Arginase activity is deficient in liver and red and white blood cells. Its activity in normal skin fibroblasts is barely detectable and is undetectable in amniotic fluid cells.Heparinized blood was obtained from five healthy fetuses between 14 and 20 weeks gestation at the time of therapeutic abortion by hysterotomy. Normal adult blood specimens were used as controls.The specific activity for the fetal specimens was 0.35-5.20 mmoles urea/gm Hb/hr compared to 3.00 in adult samples. The pH maximum of one fetal and one adult blood with Mn++ activation was 9.5-10.0. In the fetal samples, the activity with Co++ as the divalent cation was 83% that of Mn++ at pH 7.5 and 44% at pH 9.5. The comparable figures for adult blood were 96% and 63%. Activity with Ca++ and Mg++ was minimal for all specimens at pH 9.5. The apparent Km for arginine at pH 9.5 with Mn++ was 14×10−3M for two adult samples and ranged from 10-19×10−3M for four fetal specimens.Arginase in adult and fetal red cells may be specified by a single genetic locus. Therefore, fetal blood may be a suitable tissue for prenatal diagnosis of this disease.