Biochemistry - The Chemical Reactions of Living Cells, Volume 2 - D. Metzler 1980

Types of Reactions Catalyzed by Enzymes
Substitution at the Phosphorus Atom
Adenylyl Cyclase and Cyclic AMP

The formation of 3',5'-cyclic AMP (cAMP) occurs when the 3'-hydroxyl group of the ribose ring replaces the internal phosphorus atom ($ ext{P}_ ext{a}$) of ATP (stage a in the scheme below):

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The unique properties of adenylate cyclase [85] and the related guanylate cyclase [86] have already been discussed in previous chapters (Chapter 5, Section B.5; Chapter 6, Section E.5). From a kinetic standpoint, the cyclic AMP molecule is exceptionally stable; however, from a thermodynamic perspective (regarding the potential Hydrolysis of this compound), it is unstable. Specific phosphodiesterase catalyzes the Cleavage of cAMP to yield 5'-adenylic acid [AMP; stage b in equation (7-25)]. Two successive reactions in equation (7-25) account for the formation and degradation of cAMP. Note the striking similarity between this reaction sequence and the two Stages of the reaction (7-19) catalyzed by Ribonuclease.



Last update: 06/08/2026

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