Catalyzes specifically the phosphorylation of ceramide to form ceramide 1-phosphate. Possesses high activity on ceramide analogs (C6, C8 synthetic ceramides) and lower activity on C6 and C8 dihydroceramides. Has weak activity on natural ceramides (a mixture of ceramides from bovine brain) and the synthetic substrate C2 ceramide. Has very poor activity on diacylglycerol and sphingosine. Ceramide is a critical sphingolipid metabolite that induces programmed cell death (PCD) in plants and ceramide-1-phosphate has a PCD suppressive effect. Thus, ceramide phosphorylation plays a role in the modulation of PCD and CERK activity is crucial for the maintenance of cell viability. an N-acylsphing-4-enine + ATP = ADP + an N-acylsphing-4-enine 1-phosphate + H(+) Optimum pH is 8.2 (at 30 degrees Celsius). By infection with bacterial pathogen P.syringae. Enhanced apoptotic-like cell death late in development.