Activity lactosylceramide

Lipid extracts (0.3ml) were dried under nitrogen, resuspended in a<15ii1 C M (1 1) and spotted on activated silica gel 60 plates with purified glycolipid standards GM3, GM2, lactosylceramide (LC) and glucosylceramide (GC) containing 10yg sialic acid each. 

HeLa cells were cultured for 24 hr with (open bars) and without (closed bars) 5 mM sodium butyrate, harvested, and assayed for indicated enzyme activity. A GM3-sialidase activity assayed with GM3 specifically labeled with [,iC]- N-acetylneuraminic acid as substrate ("14JJ. B Sialyltrasferase activity assayed with CMP-[, acetylneuraminic acid and lactosylceramide as substrates, and synthesis of labeled GM3 determined (17). Data... 

Table I. The Effect of Various Compounds Implicated in the 2-Stage Theory of Carcinogenesis on CMP-NeuAc lactosylceramide Sialyltransferase Activity in Human Epithelial Carcinoma with (KB) Cells...

Table III. Comparison of Serum-induced ODC Activity with CMP-NeuAc lactosylceramide Sialyltransferase Activity in Various Cell Lines...

Measurement of UDP-Gal lactosylceramide galactosyltransferase Activity in Normal and Mutant Cells... 

Uridine diphosphate galactose lactosylceramide galactosyltransferase activity in cultured normal and familial hypercholesterolemic human fibroblasts... 

Very little of 7T H7-galactose precursor was converted to a glucocerbroside or to a lactosylceramide under these culture conditions (21). The activities of the sulfotransferase and galactosyltransferase, enzymes responsible for the synthesis of the myelin-associated sulfo- and glycolipids, were also measured at different days in culture (fig. 4). The activities of these enzymes in homogenates of cells derived from the 15 day embryo were relatively low at 8 days but increased until reaching... 

Figure 6. Effect of CMP-NeuAc concentration (V/S), of pH (V/pH), of enzymatic protein concentration (V/protein), and of incubation time (V/t) on the activity of synaptosomal membrane-bound sialyltransferase. Calf brain cortex. Acceptor substrates for sialyltransf erase (if) lactosylceramide ( ) desialylated fetuin (%) endogenous glycoprotein (endogenous glycolipids.

Whereas the activities of CMP-NeuNAc lactosylceramide sialyltransferase increase postnatally (38), the activities of the CMP-NeuNAc glycoprotein sialyltransferase decline dramatically during early development (17). Separate regulatory controls on the glycoprotein and glycolipid metabolism have also been implicated in a study on the brain tissues of Tay-Sachs disease patients. 

Zschoche A, Furst W, Schwarzmann G, San-hoff K (1994) Hydrolysis of lactosylceramide by human galacrtosylceramidase and GM1-/1-galactosidase in a detergent-free system and its stimulation by sphingolipid activator protein, sap-B and sup-C. Activator proteins stimulate lactosylceramide hydrolysis. Eur J Biochem 222 83-90... 

Fig. 17.3 Structures and degradation of GM2 and GA2 glycolipid. In normal cells, IV-acetylgalactosamine terminating GM2 ganglioside and its asialo-derivative GA2 are hydrolysed to GM3 and lactosylceramide respectively, by hexosaminidase. Deficiencies in hexosaminidase activity results in the accumulation of GM2 and GA2 GalNAc A-acetylgalactosamine Gal galactose Cer ceramide NeuAc sialic acid...

Fig. 17.6 Partial GSL degradation pathway. GM2 is degraded by hexosaminidase A (Hex A) in cooperation with GM2 activator protein to form GM3. The presence of a specific sialidase in mice prevents accumulation of this glycohpid in GM2 gangliosidosis and degrades its substrate to GA2, which in turn can be degraded by Hex A or B. GM3 is acted on by sialidase, present in mouse and human, and lactosylceramide (LacCer) is formed which is then further degraded by specific hydrolases...

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