Sialyltransferases in Young Rat Brain

Dain, Joel A.; Ng, Sai-Sun

doi:10.1007/978-1-4684-7844-0_23

Cited by 2 publications

(1 citation statement)

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“…This problem has been approached previously with different methodology. Indications of separate synthases for GM3 and GDla were obtained in young rat brain [24]. In embryonic chicken brain, GD3 synthase activity was found to differ from both GM3 and GDla synthase activity with respect to heat inactivation [25].…”

Section: Discussionmentioning

confidence: 99%

Ganglioside biosynthesis in rat liver

Busam

Decker

1986

European Journal of Biochemistry

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Three sialyltransferase activities involved in ganglioside biosynthesis were studied in Golgi-enriched preparations of rat liver: the formation of GM3, GD3 and GDI,. The conditions for the quantitative assays of these enzymatic reactions were standardized and optimized, with Triton X-100 being used as detergent. The apparent K,,, values of each sialyltransferase for N-acetyl-Z( 5'-cytidylyl)neuraminic acid (1.5 mM with GM3 synthase, 0.2 mM with GD3 synthase, and 0.5 mM with GDla synthase) and the respective glycolipid substrates (0.08 mM for lactosylceramide, 0.1 mM for GMJ, and 0.5 mM for G M~) were determined. Competition experiments showed that the three sialyltransferase activities are three individual catalytic entities. Moreover, evidence was found that product inhibition may play a role in the regulation of the activity of sialyltransferases.Gangliosides are sialic-acid-containing glycosphingolipids and have been found in every mammalian tissue so far examined Gangliosides are synthesized by stepwise transfer of monosaccharides and sialic acid from nucleotide-bound donors to glycolipid acceptors [A. The glycosyltransferases catdyzing these reactions are membrane-bound. In rat liver they have been found predominantly in the Golgi apparatus [8]. Up to now five transferase activities in rat liver have been characterized : two galactosyltransferases (GLZ and GMl synthase) [9], one N-acetyl-D-galactosaminyltransferase (GMZ synthase) [lo] and two sialyltransferases (GMS [ll] and GD3 [12] synthase). It has already been shown that the syntheses of lactosylceramide and G,, in rat liver are catalyzed by different enzymatic entities [9]. The specificity of the sialyltransferases with regard to the glycolipid acceptor is focused in this study. Kinetic data and an optimized assay for GDla synthase are presented as well as modifications of the already reported assays of GM3 and GD3 synthase. Modifications were required to perform substrate competition experiments. They were designed to show whether the three synthase activities can be attributed to three distinct enzyme entities. MATERIALS AND METHODS ChemicalsCytidine 5-rnonophospho-N-a~etyl-[4,5,6,7,8,9-'~C]neuraminic acid (351 Ci/mol) and UDP-~-[U-'~C]galactose (320 Ci/mol) were obtained from Amersham Buchler (Braunschweig). Sodium cacodylate, Triton X-100, PPO and POPOP were purchased from Roth (Karlsruhe). CMP-NeuSAc, NeuSAc and dithioerythritol were from Sigma (St Louis, MO, USA). All fine chemicals, coenzymes and enzymes were from

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Section: Discussionmentioning

confidence: 99%