Effect of Preparation Method on the Induction of (Sodium + Potassium) –Activated Adenosine Triphosphalase from Sugar Beet Root and its Lipid Composition

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Abstract
The (Na++K+)–stimulation of the ATPase activity in a paniculate fraction from sugar beet roots was compared after inducing treatments with dithiothreitol (DTT), cystein or deoxycholate (DOC). Protection of SH groups by cystein or DTT increased the specific activity at the optimal Na: K ratio (25 :25 mM) with a factor of about 5 as compared to the untreated fraction, and with a factor of about 3 as compared to particles treated with DOC. DTT acted chiefly at the optimum ratio of Na : K (25 :25 mM), whereas a less specific stimulation at any proportion of the couple Na : K was observed after treatment with DOC or cystein. A combined treatment (DOC + DTT) led to inactivation of the DTT effect.Treatment with DTT resulted in a loss of lipids, which were replaced by water, but otherwise little swelling took place. The loss of lipids was almost exclusively due to loss of phospholipids, and among these the zwitterkonic phos–phatidyl choline and phosphatidyl ethanolamine were affected more than the acidic phosphatidyl glycerol or phosphatidyl inositol. The sulfolipid was maintained within the particles. The combined treatment “with (DOC + DTT) led to further losses of lipid material at the same time as strong swelling took place. As compared to the treatment with DTT alone, the additional loss of lipids occurred mainly from the (sterol glycoside + cerebroside + digalactosyl diglyceride –fraction) and from the solfolipid, with some losses also from the (pigments + neutral), phosphatidyl choline and phosphatidyl glycerol fractions.The results are in agreement with our earlier data, which also show that lipid fractionation is important for the revealing of (Na+ 4– K+)–stimulated ATPase activity, possibly because of the negative electric charge of the sulfolipid, which is characteristic for the induced preparations and which may be connected with the specific site of stimulation by the cations.