Lysosomal Enzymes in Human Peripheral Blood Mononuclear Cells and Granulocytes

Abstract

Lysosomal enzymes are crucial for the degradation of numerous macromolecular substrates. Deficiencies of many of the known lysosomal enzyme activities have been associated with different clinical disorders, collectively termed the lysosomal storage diseases (1)(2)(3)(4). Accurate measurement of lysosomal enzyme activities, therefore, is important in establishing diagnoses of lysosomal storage diseases. In addition, accurate measurement of these lysosomal enzymes is critical in identifying carriers or heterozygotes for these conditions and in monitoring patients with these diseases who have undergone bone marrow transplantation and other enzyme replacement therapies. Clinical laboratories that measure lysosomal enzyme activities typically use sonicates or detergent extracts of mixed leukocyte pellets for enzymologic studies of lysosomal disorders. The use of peripheral blood leukocytes for this purpose has the merit of using a readily accessible tissue that, in addition, has considerable concentrations of most lysosomal enzymes. There are few reported analyses of the comparative activities of human lysosomal enzymes in different types of leukocytes. Limited and conflicting data have been published regarding lysosomal enzyme activities in the different populations of human peripheral leukocytes. Differences in the activities of lysosomal enzymes among populations of leukocytes, if real and of substantial magnitude, could be important clinically. In this study we comparatively analyzed six commonly measured lysosomal enzymes of clinical importance. Our data indicate significant differences in the activities of these enzymes in the different types of leukocytes. The lysosomal enzymes studied here were assayed by standard methods (below). All 4-methylumbelliferyl glycoside and nitrocatechol substrates, 4-methylumbelliferone, and buffer reagents were obtained from Sigma Chemical Co. Tissue culture reagents and fetal calf serum were purchased from Gibco BRL Products-Life Technologies. Ficoll-Paque was purchased from Pharmacia Biotech AB. Blood was obtained from healthy adult donors with informed consent. Leukocytes were fractionated with Ficoll-Paque as follows: Blood (10 mL) …