Studies on phospholipase C from Pseudomonas aureofaciens. II. Further studies on the properties of the enzyme.

Phospholipase C [EC 3.1.4.3] from Pseudomonas aureofaciens was found to be inhibited by chelating reagents such as ethylenediaminetetraacetate [EDTA] and o-phenanthroline. The inhibition was reversed by the addition of Zn2+ and, to a lesser extent, by Co2+ and Mn2+. On isoelectric focusing, the isoelectric point of this enzyme proved to be 6.3--6.5, with a single peak. The enzyme reaction with the substrate was followed in media containing an organic solvent such as diethyl ether or diethyl ether-ethyl alcohol. When ethyl alcohol was added (up to 2%) to the reaction mixture in ether, there were no marked changes in the hydrolytic rates of phosphatidylcholine and phosphatidylethanolamine. However, the enzyme activity was inhibited when the alcohol concentration was increased above 2%. In 98% diethyl ether-2% ethyl alcohol, phosphatidylcholine was hydrolyzed more rapidly than phosphatidylethanolamine, in contrast with the result obtained in water. In the single micelle state, phosphatidylethanolamine was hydrolyzed more rapidly than phosphatidylcholine or lysophatidylcholine. Acidic phospholipids and sphinogomyelin were not hydrolyzed. When the enzyme was incubated with phospholipid mixture extracted from Ps aureofaciens and rat liver, both phosphatidylethanolamine and phosphatidylcholine were hydrolyzed more rapidly than in the single micelle state of these substrates.