Purine nucleotide catabolism deamination

Purine nucleotide catabolism is outlined in Figure 15.12. There is some variation in the specific pathways used by different organisms or tissues to degrade AMP. In muscle, for example, AMP is initially converted to IMP by AMP deaminase (also referred to as adenylate aminohydrolase). IMP is subsequently hydrolyzed to inosine by 5 -nucleotidase. In most tissues, however, AMP is hydrolyzed by 5 -nucleotidase to form adenosine. Adenosine is then deaminated by adenosine deaminase (also called adenosine aminohydrolase) to form inosine. 

Guanylate reductase, which deaminates this nucleotide, catalyzes a reductive, rather than hydrolytic, deamination and has been discussed in Chapter 9. Like adenylate deaminase, it has a catabolic role and also functions in purine nucleotide interconversion. A guanosine deaminase has recently been identified in a pseudomonad (13), but it is not known to occur in animal cells. 

The catabolism of pyrimidine nucleotides, like that of purine nucleotides (Chapter 10), involves dephosphorylation, deamination, and glycosidic bond cleavage. In contrast to purine catabolism, however, the pyrimidine bases are most commonly subjected to reduction rather than to oxidation. An oxidative pathway is found in some bacteria however. 

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