Abstract
The full-length genomic DNA of MCAT (Malonyl-CoA:acyl carrier protein transacylase) in Brassica napus was cloned. BnMCAT shares very high identity with AtMCAT in gene sequence and gene structure. A multiple alignment of the protein sequence showed that BnMCAT shares high identity with other MCATs from E. coli and plants. BnMCAT was expressed in all tissues, such as roots, stems, leaves, flowers, and seeds, and no significant differences in the expression level were found in different embryo stages after pollination. According to an in vitro relative activity analysis, purified recombinant BnMCAT expressed in E. coli had transacylase activity. Although the relative activities of BnMCAT in crude extracts isolated from different staged embryos were similar and showed little variation, a higher relative activity was found in a crude extract isolated from embryos in comparison to leaves. Different relative activities of BnMCAT in crude extracts isolated from cultivars with different oil content were also found, suggesting that the activity of BnMCAT might be a decisive factor for a high oil content. Together, these results showed that BnMCAT is an important enzyme in the FAS system and indicate that BnMCAT might be a new target enzyme for future crop improvement through genetic engineering.
Highlights
Fatty acid biosynthesis is catalyzed by different enzymes, depending on the species
In the type II (Fatty acid synthesis II, FAS II) system found in most bacteria and plants, the biosynthesis of fatty acids is catalyzed by a series of small soluble proteins that are each encoded by discrete genes [1]
malonyl-CoA:acyl carrier protein transacylase (MCAT) is a key enzyme in the plant fatty acid biosynthesis pathway, and MCAT cDNA sequences have been isolated from a number of plants, such as Arabidopsis thaliana, Perilla frutescens, Capsicum annuum, Oryza sativa, and Arachis hypogaea
Summary
Fatty acid biosynthesis is catalyzed by different enzymes, depending on the species. These enzymes can be divided into two types. In the type I (Fatty acid synthesis I, FAS I) system found in many eukaryotes, the biosynthesis of fatty acids is catalyzed by a single large and multifunctional polypeptide. In the type II (Fatty acid synthesis II, FAS II) system found in most bacteria and plants, the biosynthesis of fatty acids is catalyzed by a series of small soluble proteins that are each encoded by discrete genes [1]. Malonyl-ACP is the two-carbon donor required for the elongation steps in fatty acid biosynthesis. MCAT can provide acyl-ACP thioesters for the biosynthesis of aromatic polyketides, including the largest classes of secondary metabolites, such as tetracyclines and erythromycins [3] [4]
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