Laboratory detection of aspartylglycosaminuria

Abstract

New specific methods for laboratory detection of a lysosomal storage disease aspartylglycosaminuria were developed. Aspartylglucosamine, the main metabolite accumulating in the body fluids and tissues in the disease, was measured with high-performance liquid chromatography in urine of aspartylglycosaminuria patients, carriers of the disease and normal controls as well as in amniotic fluid of normal pregnancies and one with the fetus affected by aspartylglycosaminuria. In the diseased patients, the aspartylglucosamine excretion was over 1,000-fold elevated compared to that in the carriers and controls. In the pregnancy with the fetus affected by the disease, the concentration of aspartylglucosamine was only slightly elevated, but lower than that in urine of normal individuals. As a conclusion, the determination of aspartylglucosamine in urine allowed postnatal detection of aspartylglycosaminuria, but in amniotic fluid it was useless in prenatal detection of the disease. The activity of the deficient enzyme in aspartylglycosaminuria, aspartylglycosylaminase, was assayed with a specific gas-chromatographic method. The enzyme activity was shown to lack in plasma, lymphocytes and amniotic fluid of aspartylglycosaminuria patients and the method proved applicable for postnatal and prenatal detection of aspartylglycosaminuria. The enzyme activity in lymphocytes of the carriers fell between those in normal controls and aspartylglycosaminuria patients, and the assay could be used in carrier detection in most of the cases.