Sphingomyelinase activity levels in human peripheral blood leukocytes, using [3H]sphingomyelin as substrate: study of heterozygotes and homozygotes for Niemann-Pick disease variants.
Patients and heterozygous carriers of Niemann-Pick disease types A and B as well as the primary (genetic) sea-blue histiocyte syndrome were investigated for their leukocyte sphingomyelinase activity. In parallel, glucocerebrosidase activity was determined in all cases studied. [3H]Sphingomyelin and [14C]glucocerebroside served as substrates for sphingomyelinase and glucocerebrosidase activity measurements, respectively. Conditions for these enzymes' assays are discussed. Sphingomyelinase activity was completely absent in three cases of Niemann-Pick disease type A and significantly diminished in one patient with Niemann-Pick disease type B and two with the sea-blue histiocyte syndrome. Sphingomyelinase activity in obligatory heterozygotes of all variants investigated represented about 40 to 70% of normal activity. Nevertheless, some overlapping with normal values occasionally occurred. Interestingly, glucocerbrosidase activity was elevated in patients with Niemann-Pick disease variants.
D005962:Glucosylceramidase / Q000097:blood; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007962:Leukocytes / Q000201:enzymology*; D009542:Niemann-Pick Diseases / Q000201:enzymology* / Q000235:genetics; D010727:Phosphoric Diester Hydrolases / Q000097:blood*; D013108:Sphingomyelin Phosphodiesterase / Q000097:blood*; D013109:Sphingomyelins; D013696:Temperature; D013997:Time Factors
D013109:Sphingomyelins; D010727:Phosphoric Diester Hydrolases; D013108:Sphingomyelin Phosphodiesterase; D005962:Glucosylceramidase