AbstractPhosphatidylcholine (PC)-specific phospholipase C (PC-PLC) (EC 3.1.4.3) and phosphatidylethanolamine (PE)-specific PLC (PE-PLC) (EC 3.1.4.62), which generate diacylglycerol (DG) and are tricyclodecan-9-yl-xanthogenate (D609)-sensitive, were detected both in detergent-insoluble fractions and in cytosolic fractions of mammalian tissues approximately 70 and 35 years ago, respectively. However, the genes and proteins involved in PC-PLC and PE-PLC activities remain unknown. In a recent study, we observed that mammalian sphingomyelin synthase-related protein (SMSr) display PC-PLC and PE-PLC activities in vitro. In the present study, we showed that human SMS isoforms (SMS1 and SMS2), which are located in detergent-insoluble fractions, also possesses PC-PLC activity, PE-PLC activity, and ceramide phosphoethanolamine synthase (CPES) activity in addition to SMS activity in vitro. Moreover, to identify cytosolic PC-PLC/PE-PLC, we searched the candidate PLC proteins that catalytic motif of SMSs are conserved in by BLAST search. We found that two orphan phosphatases (gene name are kept a secret due to unpublished work) displayed PLC and lipid phosphate phosphatase (LPP) activity in vitro, respectively. Taken together, we identified new type of PLCs (insoluble-PC/PE-PLC and cytosolic PC/PE-PLC and cytosolic LPP. はじめにジアシルグリセロール（DG）は protein kinase C（PKC）等を活性化することで様々な細胞応答千葉大学国際高等研究基幹 / 大学院理学研究院化学研究部門生体機能化学研究室・特任助教村上 千明Chiaki MurakamiChiba University― 125 ―飽和脂肪酸含有ジアシルグリセロール代謝の新機軸- 新タイプのホスホリパーゼ C の発見 -Innovations in the Molecular Mechanism of Saturated Fatty acid-containing Diacylglycerol metabolism -Caracterization of new type of mammalian phospholipase Cs-
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