Abstract
An enzyme that transfers sialic acid from CMP-sialic acid to lactosylceramide was concentrated 40–50 times in Golgi apparatus from rat liver relative to total homogehates. This enzyme required detergents as dispersing agents. Of the numerous detergents tested, the combination Tween 80-Triton CF-54 (1 : 2, w/w) was the most effective in stimulating the reaction. Two apparent pH optima, at 6.35 and 5.5, were observed. The enzyme showed no requirement for a divalent cation. The K m values calculated for CMP- N-acetylneuraminic acid and lactosylceramide were 2.7 · 10 −3 and 1.3 · 10 −4 M, respectively. The enzyme could not be dissociated from Golgi apparatus fractions by treatment with ultrasound, indicating that it is tightly associated with the membrane. The newly synthesized G m3, the product of the reaction, was incorporated into or became tightly associated with the membranes of the Golgi apparatus.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism
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