Nucleotide sequence encoding carbamoyl phosphate synthetase II

Chemistry: molecular biology and microbiology – Vector – per se

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435 691, 4351723, 435194, 536 231, 536 232, 536 237, C07H 2104, C12N 1530, C12N 1552, C12N 1570

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active

058495738

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BRIEF SUMMARY
This is a national phase filing of PCT application PCT/AU93/00617, filed Dec. 2, 1993.
The present invention relates to nucleotide sequences encoding carbamoyl phosphate synthetase II of Plasmodium falciparum, to methods of producing this enzyme using recombinant DNA technology and to the use of this sequence and enzyme in the design of therapeutics.


BACKGROUND OF THE INVENTION

The urgency for the design of novel chemotherapeutic agents for the treatment of malaria has been renewed in recent times due to the evolution of human malarial parasites, primarily Plasmodium falciparum, which are resistant to traditional drugs. Research into a vaccine seems a very plausible alternative, but after years of investigation, no clinically acceptable product has come to date. At the same time, there is also an increasing decline in the efficacy of insecticides against mosquito vectors. At present, more than two-thirds of the world's population--approximately 500 million people--are thought to live in malaria areas (Miller, 1989). It ranks eighth in the World Health Organization's (WHO) list of ten most prevalent diseases of the world (270 million infections a year) and ranks ninth of the ten most deadly diseases, claiming over 2 million lives a year (Cox, 1991; Marshall, 1991). Though chiefly confined to poor nations, there are recent reports of infections in the United States (Marshall, 1991) and Australia (Johnson, 1991), and ever increasing cases of travellers' malaria (Steffen and Behrens, 1992).
Comparative biochemical studies between the malaria parasite, P. falciparum and its host have revealed differences in a number of metabolic pathways. One such distinction is that the parasite relies exclusively on pyrimidine synthesis de novo because of its inability to salvage preformed pyrimidines (Sherman, 1979). Moreover, the mature human red blood cell has no recognised requirement for pyrimidine nucleotides (Gero and O'Sullivan, 1990). Major efforts have been directed towards the development of inhibitors of the pyrimidine biosynthetic pathway (Hammond et al., 1985; Scott et al., 1986; Prapunwattana et al., 1988; Queen et al., 1990; Krungkrai et al., 1992), confirming its potential as a chemotherapeutic locus. Current research into the molecular biology of the key pyrimidine enzymes is envisioned as a powerful tool, not only to get a better understanding of the parasite's biochemistry, but also to explore specific differences between the parasite and the mammalian enzymes.
Glutamine-dependent carbamoyl phosphate synthetase (CPSII, EC 6.3.5.5) catalyses the first committed and rate-limiting step in the de novo pyrimidine biosynthetic pathway of eukaryotic organisms (Jones, 1980). Moreover, because it catalyzes a complex reaction involving three catalytic units and several substrates and intermediates, it is a very interesting enzyme to study from a biochemical point of view. The structural relationship of CPSII to other pyrimidine enzymes varies in different organisms, making it a good subject for evolutionary studies.
The paucity of material that can be obtained from malarial cultures has hampered the isolation of adequate amounts of pure protein for analysis. The difficulty in purifying CPS is further augmented by its inherent instability. Studies using crude extracts from P. berghei (a rodent malaria) revealed a high molecular weight protein containing CPS activity, which was assumed to be associated with ATCase (Hill et al., 1981), a situation also found in yeast (Makoff and Radford, 1978). However, recent analysis by Krungkrai and co-workers (1990) detected separate CPSII and ATCase activities in P. berghei. Although CPS activity has been detected in P. falciparum (Reyes et al., 1982) until this current study there is no indication of its size nor its linkage with other enzymes in the pathway.
The glutamine-dependent activity of CPSII can be divided into two steps: (1) a glutaminase (GLNase) reaction which hydrolyzes glutamine (Gln) and transfers ammonia to the site of the carbamoyl phosphate synthetase; and (2

REFERENCES:
patent: 5585479 (1996-12-01), Hoke et al.
J.P. Schofield,. "Molecular Studies on an ancient gene encoding for carbomoyl-phosphate synthetase" Clinical Science (1993), vol. 84, pp. 119-128.
H. Nyunoya et al. "Characterization and derivation of the gene encoding for mitochondrial carbamyl phosphate synthetase I of Rat" Journal of Biological Chemistry (1985), vol. 260 No. 15, pp. 9346-9356.
G. Elgar et al. "Carbamoyl phosphate synthetase (CPSase) in the PYRI1-3 multigene . . . " DNA sequence, vol. 2, (1992) Harwood Academic Publisher (UK), pp. 219-226.
C.J. Lustry et al. "Yeast carbamyl phosphate synthetase" Journal of Biological Chemistry, vol. 258, No. 23, (10 Dec. 1983), pp. 14466-14472.
Chansiri et al. "The structural gene for carbamoyl phosphate synthetase from the protozoan parasite Babesia bovis" Mol. Biochem. Parasitol. 74: 239-243, Dec. 1995.
Gewirtz et al. "Facilitating oligonucleotide delivery: Helping antisense deliver on its promise" Proc. Natl. Acad. Sci. USA 93: 3161-3164, Apr. 1996.
Sambrook et al. "Moleculear cloning: A Laboratory manual, second ed." Cold Spring Harbnor Laboratory Press. pp. 8.51-8.52. 1989.
Lewin. "Genes IV" Oxford University Press, New York. pp. 506-507, 1990.
Stull et al. Antigene, ribozyme and aptamer nucleic acid drugs: Prospects and Progress. Pharm. Res. 12(4): 465-483, Apr. 1995.

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