Glutamine phosphoribosylpyrophosphate amidotransferase

Glutamine 5-phosphoribosyl-l-pyrophosphate amidotransferase, 38 310-311 Glutamine phosphoribosylpyrophosphate amidotransferase, ground spin state variability, 38 99-100 Glutathion... 

Holmes, E.W., Wyngaarden, J.B., and Kelley, W.N. Human glutamine phosphoribosylpyrophosphate amidotransferase Two molecular forms interconvertible by purine ribonucleotides and phosphoribosylpyrophosphate. J. Biol. Chem., 248 6035,1973. 

Wyngaarden, J. B. 1972. Glutamine phosphoribosylpyrophosphate amidotransferase. In Current Topics in Cellular Regulation. 

Figure 1 depicts the important steps in purine biosynthesis de novo. The first reaction which is unique to this pathway is catalyzed by the enzyme glutamine phosphoribosylpyrophosphate amidotransferase. The substrates for this reaction are phosphoribosylpyrophosphate, or PP-ribose-P, glutamine and water and the products are phosphoribosylamine, glutamate and inorganic pyrophosphate. Data obtained from the study of many species indicate that this reaction catalyzed by amidotransferase is the rate limiting step in purine biosynthesis. Phosphoribosylamine is then converted by a series of enzymatic reactions to the parent purine ribonucleotide IMP, and IMP is subsequently converted to GMP and AI IP. 

Rowe, P.B., Coleman, M.D. and Wyngaarden, J.B. 1970. Glutamine phosphoribosylpyrophosphate amidotransferase. Catalytic and conformational heterogeneity of the pigeon liver enzyme. Biochem. 1498-1505. 

Further purification of the second fraction showed that one of its enzymic components reacted PRPP with glutamine to yield another unidentified ribose compound and equivalent amounts of glutamic acid and pyrophosphate (86, 97). 5-Phosphoribosylamine (PRA) was believed to be the unknown compoimd, since synthetic PRA replaced the biosynthetically-formed ribose derivative in the subsequent reaction with glycine and ATP to form GAR, adenosine diphosphate (ADP), and inorganic P (98). The enzyme that catalyzed the formation of PRA from glutamine and PRPP has been purified from the soluble proteins of pigeon liver and named 5-phosphoribosylpyrophosphate amidotransferase (86). Unfortunately, it was not possible to isolate the natural product of the reaction because of extreme lability of the compound. 

FIGURE 15 Examples o a + proteins, (a) Ubiquitin, (b) Papain consists of one alpha-helix and four strands of antiparallel beta-sheet, (c) ribonuclease A, and (d) N-terminal domain of E. co//glutamine phosphoribosylpyrophosphate (Prpp) amidotransferase that contains a four structural layers appa. 

Nagy, M. 1970. Regulation of the biosynthesis of purine nucleotides in Schizosaccharomyces pombe. I. Properties of the phosphoribosylpyrophosphate glutamine amidotransferase of the wild strain and of a mutant desensitized towards feedback modifers. Biochim. Biophys. Acta. 198 471-481. 

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