animal agricultural production systems are major sources of nonpoint pollution affecting quality of water sources. nitrogen has been identified as the foremost source of nonpoint water pollution  and the potential negative impacts of n have become an area of public concern. protein degradation from feed ingredients is an important factorinfluencing aa supply to the duodenum. ruminal proteolysis...

In Salmonella enterica, 5-aminoimidazole ribonucleotide (AIR) is the precursor of the 4-amino-5-hydroxymethyl-2-methylpyrimidine (HMP) pyrophosphate moiety of thiamine and the last intermediate in the common HMP/purine biosynthetic pathway. AIR is synthesized de novo via five reactions catalyzed by the purF, -D, -T, -G, and -I gene products. In vivo genetic analysis demonstrated that in the abs...

Some metabolic pathway enzymes are known to organize into multi-enzyme complexes for reasons of catalytic efficiency, metabolite channeling, and other advantages of compartmentalization. It has long been an appealing prospect that de novo purine biosynthesis enzymes form such a complex, termed the "purinosome." Early work characterizing these enzymes garnered scarce but encouraging evidence for...

Purine nucleoside phosphorylase (PNP) is a key enzyme in the purine salvage pathway, which provides an alternative to the de novo pathway for the biosynthesis of purine nucleotides. PNP catalyzes the reversible phosphorolysis of 2'-deoxypurine ribonucleosides to the free bases and 2-deoxyribose 1-phosphate. Absence of PNP activity in humans is associated with specific T-cell immune suppression....

Adenine inhibited the de novo synthesis of purines in both normal and gouty man as shown by inhibition of the incorporation of glycine-(15)N into urinary uric acid without altering the incorporation of glycine-(15)N into urinary creatinine. The diminished purine synthesis did not result in a diminution in the 24 hr excretion of uric acid. This observation was explainable in part by the prompt c...

been elucidated, although metabolic effects induced by these agents employed singly have received considerable study and have been discussed in recent reviews (5, 14, 23, 26, 28, 31, 43, 44). The metabolic alteration deemed re sponsible for the tumor-inhibitory effect of azaserine is the blockade of purine nucleotide biosynthesis de novo. Re cent evidence, however, has suggested that this site ...

6-Methylmercaptopurine ribonucleoside-5'-phosphate (MeSPuRMP), the sole metabolite of 6-methylmercaptopurine ribonucleoside (MeSPuRib), is a strong inhibitor of purine de novo synthesis, inducing depletion of intracellular purine nucleotides and subsequent cell death in several tumor cell lines. In this study prevention of MeSPuRib cytotoxicity by compounds of the purine salvage pathway was stu...

Summary Ascospores generated during sexual reproduction are the primary inoculum for wheat scab fungus Fusarium graminearum . Purine metabolism is known to play important roles in fungal pathogens but its lifecycle stage‐specific regulation unclear. By characterizing genes involved purine de novo and salvage biosynthesis pathways, we showed that syntheses of inosine, adenosine guanosine monopho...

By BERTRAM A. Lowi’ AND MARJORIE K. WILLIAMS T HE MATURE human erythrocyte, which is incapable of de novo purine nucleotide synthesis, can utilize preformed purines and purine nucleosides for tile formation of purine nucleotides, in vitro.” 2 Studies in this laboratory have demonstrated that adenine is an effective precursor of the ATP of the human erythrocyte and that hypoxanthine, guanine, an...