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ThermusQ> Pathway> PWEA0002

Description

The purine nucleotide biosynthetic pathway is essentially common to most organisms. In terms of DNA replication and metabolism, the existence of a nucleotide biosynthetic pathway is necessary for the establishment of an organism, so it is important to investigate the establishment of this pathway in the early stages of life in order to consider the evolution of life. The purine nucleotide biosynthetic pathway has been investigated by Buchanan and colleagues in the 1950s and 1960s. By injecting pigeons with various isotope-labelled compounds and analyzing which atoms of the excreted uric acid were labelled. These researches determined which compound each atom of the purine ring was derived from. The purification of the enzymes involved in each reaction and the determination of the structures of the reaction intermediates were then carried out in sequence, and the reaction mechanism of the enzymes was also investigated.
The purine nucleotide biosynthetic pathway consists of a total of 14 reactions, starting from 5-phosphoribosyl-1-pyrophosphate (PRPP), via inosine monophosphate (IMP), to adenosine monophosphate (AMP) and guanosine monophosphate (GMP). In E. coli, there are two enzymes (PurN and PurT) involved in the third reaction, using N10-formyltetrahydrofolate and formic acid as substrates, respectively. In contrast, in Thermus thermophilus, only PurN is involved in this step. For the sixth reaction, two enzymes, PurE (Class I) and PurK, are involved in some eubacteria (even in Thermus thermophilus), plants, yeasts and archaea, while in other eukaryotes and archaea, PurE (Class II) alone is known to be responsible for the reaction. In some species, PurL, involved in the fourth reaction, is divided into three subunits, PurQ, PurL and PurS (even in Thermus thermophilus), while GuaA, involved in the fourteenth reaction, is divided into two subunits, GuaA1 and GuaA2.


References

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