Rat Plasma Clearance Rate and Organ Distributionof 13-Hexosaminidase lsoenzymes from Human Serum

p-Hexosaminidase (EC 3.2.1.30) is markedly increased in human serum in liver disease, chronic alcoholism, and pregnancy. Knowledge of the clearance rate of plasma! serum #{237}3-hexosaminidase is n cessary to evaluate this increase. We studied the plasma clearance of p3-hexosaminidase isoenzymes (purified from human serum and placenta) after their infusion into rat circulation. A recently developed enzyme immunoassay method was used to measure the human 13-hexosaminidase isoenzymes; this method relies on both immunoreactivity and enzyme activity, so intact human isoenzymes were measured. In comparison with the placental isoenzymes (t112 <2 mm), the serum forms showed a considerably slower clearance (t112= 2-4 h). However, desialylation of the serum forms resulted in their rapid clearance (f112<2 mm). The organ localization of the enzyme eliminated from the circulation was investigated24 h after infusion. Placental and native serum isoenzymes accumulated mainly in the liver and the spleen. Desialylated serum forms were almost exclusively localized to the liver.