Figure 2. Stage-specific expression of Pfscd and stearoyl-CoA desaturase activity in P. falciparum.

(A) Transcriptional profile of Pfscd (PFE0555w) as determined using quantitative RT-PCR. Total mRNA from synchronized P. falciparum was extracted every 6 hrs for one complete cycle (48 hrs). The mRNA was reverse-transcribed and the cDNA subjected to quantitative PCR using Pfactin as a reference gene. Results are expressed as transcript copy numbers, presented as the mean±SEM of 2 independent experiments performed in triplicate. (B) In vivo stearoyl-CoA desaturase activity. Various parasite stages were labeled with [¹⁴C]-stearic acid for 4 hrs either at 4°C or 37°C prior to extraction of the fatty acid methyl esters (FAMEs). Equal volumes of each sample (30%) were loaded on the TLC plate and resolved using petroleum ether/diethyl ether (17/3, v/v). C_18:0 and C_18:1 methyl esters were used as standards (indicated by arrowheads). Autoradiograms were exposed overnight to a Kodak Biomax MR film to reveal [¹⁴C]-labeled FAMEs. This autoradiogram is representative of results obtained in two independent experiments. (C) Substrate specificity of PfSCD. Schizonts were labeled with either radiolabeled palmitic acid (C_16:0) or stearic acid (C_18:0) for 4 hrs at 37°C. Following extraction, equal volumes were loaded on a TLC plate and FAMEs were resolved along with C_18:0 and C_18:1 methyl esters as standards using petroleum ether/diethyl ether (17/3, v/v). These were revealed after overnight exposure to a Kodak Biomax MR film.