Sphingomyelin synthase that primarily contributes to sphingomyelin synthesis and homeostasis at the plasma membrane. Catalyzes the reversible transfer of phosphocholine moiety in sphingomyelin biosynthesis: in the forward reaction transfers phosphocholine head group of phosphatidylcholine (PC) on to ceramide (CER) to form ceramide phosphocholine (sphingomyelin, SM) and diacylglycerol (DAG) as by-product, and in the reverse reaction transfers phosphocholine from SM to DAG to form PC and CER (PubM

Cell membraneGolgi apparatus membrane

Calvarial doughnut lesions with bone fragility

A rare autosomal dominant bone disease characterized by low bone density, distinctive X-ray translucencies of the skull, multiple fractures, elevated serum alkaline phosphatase, and dental caries. Patients present with childhood onset of primary osteoporosis and typical sclerotic doughnut-shaped lesions in the cranial bones.