Acyl-ACP thioesterases from macadamia ( Macadamia tetraphylla) nuts: Cloning, characterization and their impact on oil composition

• Published in: Plant physiology and biochemistry 2011, Vol.49 (1), p.82-87
• Main Authors: Moreno-Pérez, Antonio J., Sánchez-García, Alicia, Salas, Joaquín J., Garcés, Rafael, Martínez-Force, Enrique
• Format: Article
• Language: English
• Subjects: Acyl Carrier Protein - metabolism; Acyl-ACP thioesterase; Asclepic acid; Beaumont; Biological and medical sciences; Cate; Cloning, Molecular; Escherichia coli; Fatty Acids - metabolism; Fundamental and applied biological sciences. Psychology; Macadamia - classification; Macadamia - genetics; Macadamia - metabolism; Macadamia tetraphylla; Nuts - chemistry; Nuts - classification; Nuts - metabolism; Palmitoleic acid; Plant Oils - metabolism; Plant physiology and development; Recombinant Proteins - chemistry; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Species Specificity; Substrate Specificity; Thiolester Hydrolases - chemistry; Thiolester Hydrolases - metabolism
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2010.10.002

The mechanisms by which macadamia nuts accumulate the unusual palmitoleic and asclepic acyl moieties, which constitute up to 20% of the fatty acids in some varieties, are still unknown. Acyl–acyl carrier protein (ACP) thioesterases (EC 3.1.2.14) are intraplastidial enzymes that terminate the synthesis of fatty acids in plants and that facilitate the export of the acyl moieties to the endoplasmic reticulum where they can be used in the production of glycerolipids. Here, we have investigated the possible role of acyl-ACP thioesterase activity in the composition of macadamia kernel oil. Accordingly, two acyl-ACP thioesterases were cloned from developing macadamia kernels, one of the FatA type and the other of the FatB type. These enzymes were heterologously expressed in Escherichia coli, and the recombinant thioesterases were purified, characterized kinetically and assayed with a variety of substrates, demonstrating the high specificity of macadamia FatA towards 16:1-ACP. Acyl-ACP thioesterase activity was also characterized in crude extracts from two different varieties of macadamia, Cate and Beaumont, which accumulate different amounts of n-7 fatty acids. The impact of acyl-ACP thioesterase activities on the oil composition of these kernels is discussed in the light of these results. ► Cloning and characterization of acyl-ACP thioesterases cDNAs from macadamia nuts for the first time. ► Biochemical characterization of purified acyl-ACP thioesterases obtained by heterologous expression. ► Results point to acil-ACP thioesterase FatA activity as an important factor for palmitoleic acid accumulation in the oil of macadamia nuts.