The enzymic synthesis of GM1b: rat‐brain CMP‐N‐Acetylneuraminic acid: Asialo‐GM1 sialyltransferase

Yip, Morris C.M.; Nguyen, Nam

doi:10.1007/bf02534925

Cited by 5 publications

(1 citation statement)

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“…Both SAT-1 and SAT-3 are involved in the synthesis of the two major lymphocyte gangliosides II3NeuAc-LacCer (GM3) and IV3nLc4, respectively. Although GgOse4Cer was used as the exogenous acceptor in the assay for SAT-3, convincing evidence indicates that both nLcOse4Cer and GgOse4Cer are equally effective acceptors for SAT-3 Yip & Nguyen, 1981). Although the precise biological functions of glycosphingolipids remain to be determined, substantial evidence indicates important roles for them in a variety of cell surface phenomena including receptors for hormones, intercellular recognition and adhesion, growth control, and immunoregulation (Hakomori, 1981;Fishman & Brady, 1976).…”

Section: Discussionmentioning

confidence: 99%

Effects of lectin activation on sialyltransferase activities in human lymphocytes

Basu¹,

Whisler²,

Yates³

1986

Biochemistry

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The effects of phytohemagglutinin (PHA) stimulation on the activities of sialyltransferase 1 (SAT-1), and sialyltransferase 3 (SAT-3), in human lymphocytes were investigated in vitro. For SAT-1 and SAT-3, respectively, the apparent Km values with variable CMP-NeuAc concentrations were 0.19 and 0.015 mM and with variable LacCer were 0.075 and 0.17 mM. Progressive increases in the activities of SAT-1 and SAT-3 were detected in lymphocytes stimulated with PHA, whereas no increase was observed in control lymphocytes incubated in culture medium alone. These increased activities occurred within 18-36 h of incubation and preceded optimum lymphocyte proliferation. Intact lymphocytes were needed for the lectin-stimulated increase of sialyltransferase activities because neither concanavalin A nor phytohemagglutinin added to the broken cell preparation modulated SAT-1 activity. The glycolipid products formed as a result of these enzymatic reactions in the presence of endogenous and exogenous acceptors were tentatively identified by thin-layer chromatography and autofluorography. The addition of exogenous LacCer to the SAT-1 assay resulted in the radiolabeling of a small amount of ganglioside GM1b (3.4%), but GM3 was the major labeled product (96%). When GgOse4Cer was added to the SAT-3 assay, 32% GM3 and 24.6% GM1b were detected while 44% consisted of glycolipids not labeled in assays performed without exogenous acceptors. Of the radioactivity transferred to endogenous acceptors, 81.3% was in GM3 and 14.6% in GM1b. These results demonstrate that the modulation of sialyltransferase activity occurs earlier than cellular activation.

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Section: Discussionmentioning

confidence: 99%