Sialyltransferase endogenous

Minus endogenous values CMP-NeuAc lactosylceramide sialyltransferase... 

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.

Kinetic Properties of Sialyltransferases. The sialyl-transferase activities with the endogenous glycoprotein and glycolipid acceptors in the standard assays (15) were linear with time for at least 60 min, while those with the exogenously added GMi and DS-fetuin were linear with time only for about 30 min (Figure 1). Activities were directly proportional to the amount of enzyme added up to 0.75 mg protein/assay (Figure 2). 

Figure 3. (a) Distribution of endogenous sialyltransferase activities on continuous... 

Figure 4. Effects of nonionic detergents on sialyltransferase activities. X. Endogenous glycoproteins A, exogenous DS-fetuin O, endogenous glycolipids O, exogenous GM, (16).

Values are the mean of two experiments. Absolute values per g of brain were ganglioside NeuNAc, 1.4 /imol endogenous acceptor capacity (E A C), 245.616 cpm of n-NeuNAc incorporated into endogenous gangliosides after 60 min of incubation of membranes with CMP- H-NeuNAc CMP-NeuNAc lactosylceramide sialyltransferase activity (STA), 3,380,951 cpm of H-NeuNAc incorporated into lactosylceramide after 60 min of incubation with CMP-3H-NeuNAc. Relative concentration (RC) means ... 

The sialyltransferase transfers H-sialic acid from CMP-N- H-acetylneuraminic acid to endogenous IgG acceptor and to exogenous acceptor prepared by treating rabbit IgG with neuraminidasa Both the transferase and the endogenous product are bound to the microsome fraction. 

The demonstration of endogeneous glycoprotein sialyltransferase activity represents a composite of secretory glycoproteins, still membrane-bound during their biosynthesis, and genuine membrane glycoprotein precursors. Thus, no... 

Sialyltransferase activities in normal and virally transformed mouse 3T3 cells have also been measured with specific endogenous acceptors (Bosmann, 1972a). The acceptors were prepared by incubating the intact cells with neuraminidase and then trypsin. The desialylated material released from the cells was used to measure sialyltransferase activity in crude detergent extracts of the cells. Cells transformed by MSV, RSV, or Py had more acceptor and transferase activity than normal 3T3 cells. Surface sialyltransferase activity as measured by the ability of intact cells to transfer sialic acid- C from CMP-NANA- C to undefined surface acceptors was also higher in the transformed lines (Bosmann, 1972 ). 

---