1-(9Z-octadecenoyl)-sn-glycero-3-phospho-L-serine + octadecanoyl-CoA <=> 1-(9Z-octadecenoyl)-2-octadecanoyl-sn-glycero-3-phospho-L-serine + CoA
1-(9z-octadecenoyl)-sn-glycero-3-phospho-l-serine + octadecanoyl-coa <=> 1-(9z-octadecenoyl)-2-octadecanoyl-sn-glycero-3-phospho-l-serine + coa