Studies of Isoprenoid Biosynthesis in Escherichia coli-Further clarification of metabolic pathway and it's regulation mechanism

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1.We detected two novel prenyltransferase activities in a farnesyl transferase null mutant of Escherichia coli. Although the amounts of these enzymes are slight, they are thought to substitute for the detected enzyme. They can be purified by adding a detergent into buffer solution, like membrane proteins. one of them was characterized as octaprenyl diphosphate synthase, and the other was shown to synthesize farnesyl diphosphate and longer prenyl diphosphates2.We tried to elucidate the mechanism by which prenyltransferases decided chain length of their products, aiming at production of prenyl diphosphates in Escherichia coli. Using random mutagenesis technique, we succeeded to change chain length of the products.of prenyltransferases derived from a thermophilic eubacteria and a high-degree thermophilic archaea, and revealed that an amino acid residue which locates on the fifth position before the first of two aspartate-rich motifs, which are highly conserved between prenyltransferases, is important for the mechanism of product detemination. They were the first reports on the artificial control of the product's chain length of prenyltransferases. Besides, we compared surrounding regions of the important amino acid residues of various prenyltransferases and mutagenized them according to the result of comparison. Therefore we found that the mechanisms of product determination of prenyltransferases can be differentiated phylogenctically.