Nucleic and amino acid sequences relating to a novel transketolase, and methods for the expression thereof

#The present invention relates to nucleic acid sequences which code for a novel transketolase from peppermint (Mentha x piperita), and to vectors containing the sequences, host cells containing the sequences and methods of upregulating or downregulating the production or activity of the transketolases and their mutants.

#The isoprenoids comprise the largest family of natural products with over 20,000 individual compounds described to date (Connolly, J. D. & Hill, R. A., Dictionary of Terpenoids (Chapman and Hall, London, 1991)). The isoprenoids play numerous functional roles in plants as hormones (gibberelins, abscisic acid), photosynthetic pigments (side chain of phytol carotenoids), electron carriers (side chain of plastoquinone), and structural components of membranes (phytosterols). Isoprenoids also serve in communication and defense, for example as attractants for pollinators and seed dispersers, and as competitive phytotoxins, antibiotics, and herbivore repellents and toxins (Harborne, J. B. in Ecological Chemistry and Biochemistry of Plant Terpenoids (Harborne, J. B., Tomas-Berbean, F. A, Eds.), pp. 399-426 (Clarendon Press, Oxford, 1991)).

#Until recently, it was generally assumed that all isoprenoids were synthesized from acetyl-CoA via the classical mevalonate pathway (Spurgeon, S. L. & Porter, J. W., Eds., in Biosynthesis of Isoprenoid Compounds, Vol. 1, pp 1-46 (John Wiley, New York, 1983)). However, in 1993, Rohmer and co-workers (Rohmer, M. et al., Biochem. J. 295:517-524 (1993)) demonstrated that a non-mevalonate pathway, originating from pyruvate and glyceraldehyde-3-phosphate (GAP) (Rohmer, M. et al., J. Am. Chem. Soc. 118:2564-2566 (1996)), operated in several eubacteria, including E. coli. Evidence subsequently emerged that the plastid-derived isoprenoids of plants, including carotenoids and the prenyl side chains of chlorophyll and plastoquinone (Lichtenthaler, H. K. et al., FEBS Lett. 400:271-274 (1997)), as well as isoprene (Zeidler J. G. et al., Z. Naturforsch 52c:15-23 (1997)), monoterpenes (Eisenreich, W. et al., Tetrahedron Lett. 38:3889-3892 (1997)) and diterpenes (Eisenreich, W. et al., Proc. Natl. Acad. Sci. USA 93:6431-6436 (1996)); (Schwarz, M. K., PhD thesis, ETH, Zurich, Switzerland (1994)), are synthesized via the pyruvate/GAP route to isopentenyl diphosphate (IPP). This new pathway had been completely overlooked in the past.

#The foregoing aspects and many of the attendant advantages of this invention will be better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

#FIG. 1 is a schematic representation of the enzymatic pathway from pyruvate to isopentenyl diphosphate IPP) as catalyzed by 1-deoxyxylulose-5-phosphate synthase (DXPS). The addition of thiamin pyrophosphate (TPP) -activated acetaldehyde, formed by decarboxylation of pyruvate, to C1 of glyceraldehyde-3-phosphate (GAP) and subsequent loss of TPP yields 1-deoxyxylulose-5-phosphate, which ultimately gives rise to isopentenyl diphosphate (IPP).

#FIG. 2A shows a GC-MS analysis of the product formed by the recombinant DXPS peppermint enzyme. Mass fragmentation patterns are illustrated for the biosynthetic product after dephosphorylation and trimethylsilylation (Rt=6.71 min).

#As used herein, the terms “amino acid” and “amino acids” refer to all naturally occurring L-α-amino acids or their residues. The amino acids are identified by either the single-letter or three-letter designations:

#Asp D aspartic acid Ile I isoleucine Thr T threonine Leu L leucine Ser S serine Tyr Y tyrosine Glu E glutamic acid Phe F phenylalanine Pro P proline His H histidine Gly G glycine Lys K lysine Ala A alanine Arg R arginine Cys C cysteine Trp W tryptophan Val V valine Gln Q glutamine Met M methionine Asn N asparagine

#As used herein, the term “nucleotide” means a monomeric unit of DNA or RNA containing a sugar moiety (pentose), a phosphate and a nitrogenous heterocyclic base. The base is linked to the sugar moiety via the glycosidic carbon (1′ carbon of pentose) and that combination of base and sugar is called a nucleoside. The base characterizes the nucleotide with the four bases of DNA being adenine (“A”), guanine (“G”), cytosine (“C”) and thymine (“T”). Inosine (“I”) is a synthetic base that can be used to substitute for any of the four, naturally occurring bases (A, C, G or T). The four RNA bases are A,G,C and uracil (“U”). The nucleotide sequences described herein comprise a linear array of nucleotides connected by phosphodiester bonds between the 3′ and 5′ carbons of adjacent pentoses.