Molecular cloning and functional expression of Perilla frutescens 3-ketoacyl-(acyl carrier protein) synthase III

The 3-ketoacyl-acyl carrier protein synthase III (KAS III) is a condensing enzyme catalyzing the initial step of fatty acid biosynthesis. We isolated two KAS III cDNA isoforms (PfKAS3a and PfKAS3b) from a cDNA library specific to Perilla frutescens immature seeds. Two cDNAs coded for 401 and 400 amino acids, respectively, which showed high degree of sequence similarity to corresponding enzymes from various sources. Results of Southern hybridization indicated that the PfKAS3a gene is present as two copies, whereas the PJKAS3b gene is a single copy. While both genes were equally expressed in high levels during early stages of seed maturation in a development-specific manner, the PfKAS3b transcript showed more prolonged appearance. Expression of the functional recombinant perilla KAS III increased the myristate level in E. coli but it exerted no appreciable effect on cell growth.