Purines and Pyrimidines
1961; Elsevier BV; Linguagem: Inglês
10.1016/b978-1-4832-2915-7.50011-x
Autores Tópico(s)Adenosine and Purinergic Signaling
ResumoThis chapter provides an overview of purines and pyrimidines and their biosynthesis. The pathways of purine and pyrimidine metabolism have been greatly aided by tracer research, nutritional and genetic studies with intact organisms, and tissue studies in vitro. The study of purine synthetic reactions was complicated by the increased formation of purine bases from the breakdown of tissue nucleic acids and nucleotides upon homogenization of the tissue. The utilization of free purines is accomplished by reaction with PRPP to form nucleotides directly. The bases have also been converted to nucleotides via the nucleosides. Nucleosides are produced by reaction of free bases with ribose 1-phosphate in the presence of nucleoside phosphorylase. The extensive utilization of dietary adenine and the nonutilization of guanine in rat have been explained in terms of the relative absence of the enzyme adenase and the presence of much guanase in rat tissues. The synthesis of purines de novo was initiated by the formation of 5-phosphoribosylamine by reaction of glutamine with 5-phosphoribosylpyrophosphate. The nucleotides that are constituents of nucleic acids, namely, guanylic acid and adenylic acid, were formed from inosinic acid.
Referência(s)