Nucleotides physiologic functions

Nucleotides participate in reactions that fulfill physiologic functions as diverse as protein synthesis, nucleic acid synthesis, regulatory cascades, and signal transduction pathways. 

Drugs interfere with a vast range of physiological functions in order to produce their pharmacological effects. Examples are the inhibition of coagulation factor synthesis (warfarin), the promotion or repression of gene expression (steroids, antisense nucleotides), inhibition of an electrolyte co-transporter... 

Beavo, J. A. (1995) Cyclic nucleotide phosphodiesterases functional implications of multiple isoforms. Physiologic Rev 75(4), 725-748. 

Nucleotides such as ATP, ADP, UTP or others have many important physiological functions in cells. Besides the energetic role of nucleotides,... 

An important difference between animal and plant electron transferring proteins is the non-exchangeability in their physiological functions adrenodoxin is inactive for photosynthetic pyridine nucleotide reduction and spinach ferredoxin does not function in adrenal steroid hydroxy-... 

Adenosine, a natural purine metabolite of adenine nucleotides, is a key regulator of many physiologic functions including vascular blood flow, platelet thrombotic... 

Adenylate kinase, which is abundant in muscle as in many other tissues, decreases in dystrophic mouse and human muscle (H6, P7). This enzyme, by interconverting adenine nucleotides, probably functions in the control of glycolysis it seems reasonable to suppose, therefore, that its activity may be governed by the same factors which influence glycolytic enzymes, as discussed above. A severe decline in the activity of AMP deaminase occurs in muscular dystrophy (P6, P7) and also in denervated muscle (M12) and in some cases of muscle affected by hypokalemic periodic paralysis (E6). Skeletal muscle normally contains a higher concentration of this enzyme than other tissues in fact, it is almost absent from some, such as liver. Its physiological function, and hence the significance of the sharp decline in its activity in diseased muscle, is still a matter of speculation. 

Walter U (1984) Cyclic-GMP-regulated enzymes and their possible physiological functions. In Greengard P et al. (Eds), Advances in cyclic nucleotide and protein phosphorylation research, 17, 249-257. 

The outline of this chapter will follow a "system s approach" to regulation of smooth muscle relaxation and will be divided into sections dealing with ion flux regulation, key protein kinases, and regulation of cyclic nucleotides. For detail on the normal biochemi-cal/physiological function of these systems, the reader is referred to Chapters 9, 11, 12, 16, 20, and 22 in this volume. Where appropriate, differences between vascular, airway, gastrointestinal, and reproductive smooth muscle will be noted. 

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