Guanylate reductase

The actual physiological role of these stimulatory and inhibitory effects of purine nucleotides on the enzymes of purine ribonucleoside interconversion is very difficult to assess, and little is knovm about the matter at the present time. Inhibition of inosinate dehydrogenase by metabolites of guanine (S6) and inhibition of guanylate reductase by metabolites of adenine (41) appear to occur in some bacteria supplied with these bases. 

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. 

Chloropurine ribonucleotide and thioinosinic acid also react covalently with GMP reductase, the enzyme that converts guanylic acid to inosinic acid and ammonia [318]. 

Figure 2 Potential relationships between NAD(P)H-derived ROS, redox systems, and signaling mechanisms regulated by PO2 in vascular smooth muscle. LDH, lactate dehydrogenase GSH red, glutathione reductase GSH Px, glutathione peroxidase RNS, reactive nitrogen species SOD, superoxide dismutases sGC, soluble guanylate cyclase MAPK, mitogen-activated protein kinases.

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