[Properties of phospholipase D from Raphanus sativus].

The main properties of phospholipase D from radish roots were studied. The effects of various activators including Ca2+ on the catalytic activity of the enzyme were determined. The necessity for Ca2+ is in a large degree dependent on the type of the prime, as well as on the substrate type. Sodium dodecyl sulfate and diethyl ester can induce lecithine cleavage in the presence of Ca2+, while solid adsorbents, e.g. silicagel, can stimulate the reaction in the absence of Ca2+. The curve of the enzyme hydrolytic activity dependence on pH has two maxima, which depend on the type of the prime. Phospholipase D from radish roots, unlike the enzyme from other plants (cotton, peanut, cabbage, etc.) displays a more pronounced specificity for lecithine as substrate and is weakly active in the reaction with cephaline. Cephaline undergoes splitting by phospholipase D in the absence of Ca2+ as well, despite the fact that Ca2+ are necessary for lecithine hydrolysis. An addition of Ca2+ increases the enzymic affinity for the substrate in all cases studied. Some data on the transalkylating function of the enzyme are given.