An isolated polynucleotide encoding a non-naturally occurring mutant polypeptide having acyl-CoA:lysophosphatidylcholine acyltransferase (LPCAT) activity, wherein said mutant polypeptide comprises at least one mutant membrane-bound O-acyltransferase protein motif selected from the group consisting of: (a) a mutant motif comprising an amino acid sequence as set forth in SEQ ID NO:33 at a position corresponding to amino acid residues 132 to 138 of SEQ ID NO:4, wherein SEQ ID NO:33 differs from SEQ ID NO:16 (M-[V/I]-L-X 2 -KL) by at least one amino acid mutation selected from the group consisting of: M1A, M1N, M1C, M1G, M1Q, M1H, M1I, M1L, M1F, M1P, M1S, M1T, M1W, M1Y, M1V, V2A, V2N, V2C, V2G, V2Q, V2H, V2L, V2M, V2F, V2P, V2S, V2T, V2W, V2Y, I2A, I2N, I2C, I2G, I2Q, I2H, I2L, I2M, I2F, I2P, I2S, I2T, I2W, I2Y, L3A, L3N, L3C, L3G, L3Q, L3H, L3M, L3F, L3P, L3S, L3T, L3W, L3Y, L3V, K6A, K6R, K6N, K6G, K6H, K6P, K6S, K6T, K6Y, L7A, L7N, L7C, L7G, L7Q, L7H, L7I, L7M, L7F, L7P, L7S, L7T, L7W and L7Y and wherein SEQ ID NO:16 corresponds to positions 132 to 138 of SEQ ID NO:4; (b) a mutant motif comprising an amino acid sequence as set forth in SEQ ID NO:34 at a position corresponding to amino acid residues 132 to 148 of SEQ ID NO: 4, wherein SEQ ID NO:34 differs from SEQ ID NO:8 (M-[V/I]-[L/I]-X 2 -K-[L/V/I]-X 8 -DG) by at least one amino acid mutation selected from the group consisting of: M1A, M1N, M1C, M1G, M1Q, M1H, M1I, M1L, M1F, M1P, M1S, M1T, M1W, M1Y, M1V, V2A, V2N, V2C, V2G, V2Q, V2H, V2L, V2M, V2F, V2P, V2S, V2T, V2W, V2Y, I2A, I2N, I2C, I2G, I2Q, I2H, I2L, I2M, I2F, I2P, I2S, I2T, I2W, I2Y, L3A, L3N, L3C, L3G, L3Q, L3H, L3M, L3F, L3P, L3S, L3T, L3W, L3Y, L3V, I3A, I3N, I3C, I3G, I3Q, I3H, I3M, I3F, I3P, I3S, I3T, I3W, I3Y, I3V, K6A, K6R, K6N, K6G, K6H, K6P, K6S, K6T, K6Y, L7A, L7N, L7C, L7G, L7Q, L7H, L7I, L7M, L7F, L7P, L7S, L7T, L7W, L7Y, V7A, V7N, V7C, V7G, V7Q, V7H, V7I, V7M, V7F, V7P, V7S, V7T, V7W, V7Y, I7A, I7N, I7C, I7G, I7Q, I7H, I7M, I7F, I7P, I7S, I7T, I7W, I7Y, D16A, D16N, D16G, D16E, D16Q, D16H, D16F, D16S, D16T, G17A, G17N, G17H, G17L, G17M, G17F, G17S, G17T and G17V and wherein SEQ ID NO:8 corresponds to positions 132 to 148 of SEQ ID No:4; and wherein the polynucleotide is operably linked to at least one regulatory sequence. (a) a mutant motif comprising an amino acid sequence as set forth in SEQ ID NO:33 at a position corresponding to amino acid residues 132 to 138 of SEQ ID NO:4, wherein SEQ ID NO:33 differs from SEQ ID NO:16 (M-[V/I]-L-X 2 -KL) by at least one amino acid mutation selected from the group consisting of: M1A, M1N, M1C, M1G, M1Q, M1H, M1I, M1L, M1F, M1P, M1S, M1T, M1W, M1Y, M1V, V2A, V2N, V2C, V2G, V2Q, V2H, V2L, V2M, V2F, V2P, V2S, V2T, V2W, V2Y, I2A, I2N, I2C, I2G, I2Q, I2H, I2L, I2M, I2F, I2P, I2S, I2T, I2W, I2Y, L3A, L3N, L3C, L3G, L3Q, L3H, L3M, L3F, L3P, L3S, L3T, L3W, L3Y, L3V, K6A, K6R, K6N, K6G, K6H, K6P, K6S, K6T, K6Y, L7A, L7N, L7C, L7G, L7Q, L7H, L7I, L7M, L7F, L7P, L7S, L7T, L7W and L7Y and wherein SEQ ID NO:16 corresponds to positions 132 to 138 of SEQ ID NO:4; (b) a mutant motif comprising an amino acid sequence as set forth in SEQ ID NO:34 at a position corresponding to amino acid residues 132 to 148 of SEQ ID NO: 4, wherein SEQ ID NO:34 differs from SEQ ID NO:8 (M-[V/I]-[L/I]-X 2 -K-[L/V/I]-X 8 -DG) by at least one amino acid mutation selected from the group consisting of: M1A, M1N, M1C, M1G, M1Q, M1H, M1I, M1L, M1F, M1P, M1S, M1T, M1W, M1Y, M1V, V2A, V2N, V2C, V2G, V2Q, V2H, V2L, V2M, V2F, V2P, V2S, V2T, V2W, V2Y, I2A, I2N, I2C, I2G, I2Q, I2H, I2L, I2M, I2F, I2P, I2S, I2T, I2W, I2Y, L3A, L3N, L3C, L3G, L3Q, L3H, L3M, L3F, L3P, L3S, L3T, L3W, L3Y, L3V, I3A, I3N, I3C, I3G, I3Q, I3H, I3M, I3F, I3P, I3S, I3T, I3W, I3Y, I3V, K6A, K6R, K6N, K6G, K6H, K6P, K6S, K6T, K6Y, L7A, L7N, L7C, L7G, L7Q, L7H, L7I, L7M, L7F, L7P, L7S, L7T, L7W, L7Y, V7A, V7N, V7C, V7G, V7Q, V7H, V7I, V7M, V7F, V7P, V7S, V7T, V7W, V7Y, I7A, I7N, I7C, I7G, I7Q, I7H, I7M, I7F, I7P, I7S, I7T, I7W, I7Y, D16A, D16N, D16G, D16E, D16Q, D16H, D16F, D16S, D16T, G17A, G17N, G17H, G17L, G17M, G17F, G17S, G17T and G17V and wherein SEQ ID NO:8 corresponds to positions 132 to 148 of SEQ ID No:4; and wherein the polynucleotide is operably linked to at least one regulatory sequence.