FIGURE 7.

Enzyme activities of plant GPCATs. A, specific activity of A. thaliana GPCAT (AtGPCAT), S. cerevisiae GPCAT (ScGPCAT), B. napus GPCAT (BnGPCAT), and R. communis GPCAT (RcGPCAT). B, acyl-CoA specificity of the RcGPCAT. The activity was measured as incorporation of ¹⁴C activity from [¹⁴C]choline-labeled GPC (4 mm) into chloroform-soluble lipids in the presence of 18:1-CoA (0.2 mm) by microsomal preparations (2 μg (A) and 4 μg (B) of protein) prepared from ale1Δ gpc1Δ yeast cells expressing the different GPCATs. Incubations with microsomes prepared from gpc1Δ transformed with empty vector gave no incorporation of radioactivity into the chloroform phase. Incubation time was 8 min (A) and 4 min (B). Data are given for triplicate assays ± S.D. (error bars). Of the ¹⁴C activity incorporated in lipids, 98–99% was recovered as lysophosphatidylcholine, and 1–2% was recovered as phosphatidylcholine.