Improved sensitivity of an acid sphingomyelinase activity assay using a C6:0 sphingomyelin substrate
نویسندگان
چکیده
Short-chain C6-sphingomyelin is an artificial substrate that was used in an acid sphingomyelinase activity assay for a pilot screening study of patients with Niemann-Pick disease types A and B. Using previously published multiplex and single assay conditions, normal acid sphingomyelinase activity levels (i.e. false negative results) were observed in two sisters with Niemann-Pick B who were compound heterozygotes for two missense mutations, p.C92W and p.P184L, in the SMPD1 gene. Increasing the sodium taurocholate detergent concentration in the assay buffer lowered the activity levels of these two patients into the range observed with other patients with clear separation from normal controls.
منابع مشابه
Reliable Assay of Acid Sphingomyelinase Deficiency with the Mutation Q292K by Tandem Mass Spectrometry.
Niemann-Pick-A/B disease is a lysosomal storage disease caused by deficiency of acid sphingomyelinase (1 ). Efforts are underway to develop novel therapies for this disease, and some newborn screening centers have started to test for acid sphingomyelinase enzymatic activity in dried blood spots on newborn screening cards. Available assays for newborn screening include tandem mass spectrometry (...
متن کاملHigh-precision fluorescence assay for sphingomyelinase activity of isolated enzymes and cell lysates.
Sphingomyelinases are important enzymes of signal transduction. They catalyze the hydrolysis of sphingomyelin, giving rise to the intracellular formation of biologically active ceramide and phosphatidylcholine. Here we report on a fluorescence method for the fast and accurate determination of this enzyme in biological samples. The assay is based on a fluorescent sphingomyelin analog carrying fl...
متن کاملEffect of saposins on acid sphingomyelinase.
The effect of saposins (A, B, C and D) on acid sphingomyelinase activity was determined using a crude human kidney sphingomyelinase preparation and a purified sphingomyelinase preparation from human placenta. Saposin D stimulated the activity of the crude enzyme by increasing its apparent Km and Vmax. values for sphingomyelin hydrolysis. Unlike the crude enzyme, the activity of the purified enz...
متن کاملTransport of sphingomyelin to the cell surface is inhibited by brefeldin A and in mitosis, where C6-NBD-sphingomyelin is translocated across the plasma membrane by a multidrug transporter activity.
Sphingomyelin is a major lipid of the mammalian cell surface. The view that sphingomyelin, after synthesis in the Golgi lumen, reaches the outer leaflet of the plasma membrane on the inside of carrier vesicles has been challenged by inconsistencies in the results of transport studies. To investigate whether an alternative pathway to the cell surface exists for sphingomyelin, brefeldin A and mit...
متن کاملIn situ assay of acid sphingomyelinase and ceramidase based on LDL-mediated lysosomal targeting of ceramide-labeled sphingomyelin.
The activity of lysosomal sphingolipid hydrolases is usually estimated in vitro from complex assays on cell lysates under artificial conditions including the presence of detergents and substrate analogs. However, the measure of their effective activity in situ (i.e., in living cells) is necessary to understand the normal intracellular sphingolipid turnover. Moreover, their determination in cell...
متن کامل