Identification of a novel Ca2+-dependent, phosphatidylethanolamine-hydrolyzing phospholipase D in yeast bearing a disruption in PLD1.

We have previously reported the identification and partial characterization of a gene encoding a phospholipase D activity (PLD1) in the yeast, Saccharomyces cerevisiae. Here we report the existence of a second phospholipase D activity, designated PLD2, in yeast cells bearing disruption at the PLD1 locus. PLD2 is a Ca2+-dependent enzyme which preferentially utilizes phosphatidylethanolamine over phosphatidylcholine as a substrate. In contrast to PLD1, the activity of PLD2 is insensitive to phosphatidylinositol 4,5-bisphosphate, and the enzyme is incapable of catalyzing the transphosphatidylation reaction with short chain alcohols as acceptors. Subcellular fractionation shows that PLD2 localizes mainly to the cytosol, but could also be detected in the particulate fraction. Thus, the biochemical properties of PLD2 appear to be substantially different from those of PLD1. PLD2 activity is significantly and transiently elevated upon exit of wild type yeast cells from stationary phase, suggesting that it may play a role in the initiation of mitotic cell division in yeast. In view of the significantly different properties of PLD1 and PLD2, and because the yeast genome contains PLD1 as the sole member of the recently defined PLD gene family, it may be concluded that PLD2 is structurally unrelated to PLD1. Thus, the novel PLD2 activity described herein is likely to represent the first identified member of a new PLD gene family.