This prototypical second messenger (FWfree-acid = 329.21 g/mol; lmax = 259 nm; eM = 15400 M–1cm–1; Abbreviation: 3’,5’-cyclic AMP, 3’,5’-cAMP, opr cAMP), the isolation of which in the late 1950s earned Earl Sutherland his share of the 1971 Nobel Prize in Medicine & Physiology, activates susceptible protein kinases in signal transduction cascades. Elevated cAMP concentrations also activate cyclicAMP-gated ion channels; Exchange Proteins Activated by cAMP (or EPAC), such as RAPGEF3; and popeye domain-containing proteins (or Popdc). While many enzymes are weakly inhibited by cAMP (with inhibition constants typically in the 0.1 mM range or above), the peak physiologic concentration of cAMP rarely exceeds 1020 μM. Target(s): phosphate-activated glutaminase; glyceraldehyde3-phosphate dehydrogenase, Ki = 0.11 mM for the yeast enzyme; choline kinase; Bacillus subtilis ribonuclease; NAD(P)+ transhydrogenase, AB-specific; phosphofructokinase, weakly inhibited; hexokinase; adenosine deaminase; NAD+ nucleosidase, or NADase; poly(ADP-ribose) glycohydrolase; GMP synthetase; 5-phosphoribosylamine synthetase, or ribose-5phosphate:ammonia ligase; tyrosyl-tRNA synthetase, weakly inhibited; adenylylsulfatase; CDP-diacylglycerol diphosphatase; nucleotide diphosphatase, weakly inhibited; ATP diphosphatase, slight inhibition; keratan sulfotransferase, weakly inhibited; adenosylhomocysteinase; 6-phospho-b-glucosidase; prenyldiphosphatase; CMP-N-acylneuraminate phosphodiesterase; 2’,3’-cyclic-nucleotide 3’-phosphodiesterase, or cCMP phosphodiesterase; 3’,5’-cyclic-GMP phospho-diesterase, or cGMP phosphodiesterase; sphingomyelin phosphodiesterase; phosphoprotein phosphatase; 5’-nucleotidase; acid phosphatase; diacylglycerol cholinephosphotransferase; ethanolaminephosphotransferase; glucose-1-phosphate adenylyltransferase; nucleoside diphosphate kinase; AMP:thymidine kinase; diacylglycerol kinase; nucleoside phosphotransferase; 1phosphatidylinositol 4-kinase; NAD+ kinase (63; procollagen glucosyltransferase64; chitin synthase, weakly inhibited; glycogen phosphorylase, weakly inhibited; luciferase, firefly (Photinus-luciferin 4-monooxygenase, ATP-hydrolyzing.
