2',3'-Cyclic-Nucleotide PhosphodiesterasesPhosphoric Diester HydrolasesPhosphodiesterase InhibitorsSulfonesNucleotidasesPurinesPhosphodiesterase 5 InhibitorsPiperazines3',5'-Cyclic-GMP PhosphodiesterasesProtease Inhibitors1-Methyl-3-isobutylxanthine3',5'-Cyclic-AMP PhosphodiesterasesCyclic Nucleotide Phosphodiesterases, Type 5RolipramErectile DysfunctionHIV Protease InhibitorsPurinones4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinoneCyclic AMPCyclic GMPCyclic Nucleotide Phosphodiesterases, Type 4TheophyllinePhosphodiesterase 3 InhibitorsMilrinonePhosphodiesterase 4 InhibitorsCyclic Nucleotide Phosphodiesterases, Type 3Penile ErectionVasodilator AgentsPapaverineSerine Proteinase InhibitorsHIV ProteasePyrrolidinonesPhosphodiesterase ICyclic Nucleotide Phosphodiesterases, Type 1ColforsinPentoxifyllineBucladesineMolecular Sequence DataPeptide HydrolasesKineticsSerine EndopeptidasesXanthinesPyridazines8-Bromo Cyclic Adenosine MonophosphateNucleotides, CyclicDose-Response Relationship, DrugAmino Acid SequenceAdenylate CyclaseEndopeptidasesCysteine EndopeptidasesCells, CulturedSecretory Leukocyte Peptidase InhibitorIsoproterenolPyrimidinonesSaquinavirRitonavirIndinavirCysteine Proteinase InhibitorsHypertension, PulmonaryTime FactorsTrypsin InhibitorsEnoximoneProteinase Inhibitory Proteins, SecretorySerpinsEnzyme ActivationNelfinavirCysteine ProteasesVinca AlkaloidsNitric OxideCalciumCell LineCyclic Nucleotide Phosphodiesterases, Type 2PenisHydrolysisProteasome Endopeptidase ComplexSignal TransductionAmrinoneCyclic AMP-Dependent Protein KinasesAlprostadilCyclic Nucleotide Phosphodiesterases, Type 6Guanylate CyclaseAminophyllineTriazinesCattleProtease NexinsBufo bufoHomosexuality, MaleEnzyme InhibitorsSubstrate SpecificityCyclic GMP-Dependent Protein KinasesCarbamatesSulfonamidesProteolysisMutationPhotoreceptor CellsVentricular Dysfunction, LeftMethamphetaminealpha 1-AntitrypsinDibutyryl Cyclic GMPRNA, Messenger