2',3'-Cyclic-Nucleotide PhosphodiesterasesPhosphoric Diester HydrolasesPhosphodiesterase InhibitorsNucleotidasesSulfonesPurinesProtease Inhibitors1-Methyl-3-isobutylxanthine3',5'-Cyclic-AMP PhosphodiesterasesPhosphodiesterase 5 InhibitorsRolipram3',5'-Cyclic-GMP PhosphodiesterasesHIV Protease InhibitorsPurinonesCyclic Nucleotide Phosphodiesterases, Type 54-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinonePiperazinesCyclic AMPCyclic Nucleotide Phosphodiesterases, Type 4Nitrate ReductaseCyclic GMPTheophyllinePhosphodiesterase 3 InhibitorsErectile DysfunctionMilrinonePhosphodiesterase 4 InhibitorsCyclic Nucleotide Phosphodiesterases, Type 3PapaverineSerine Proteinase InhibitorsHIV ProteasePyrrolidinonesPhosphodiesterase IVasodilator AgentsCyclic Nucleotide Phosphodiesterases, Type 1ColforsinMolecular Sequence DataPentoxifyllinePenile ErectionBucladesineKineticsPeptide HydrolasesSerine EndopeptidasesXanthinesAmino Acid SequenceDose-Response Relationship, DrugPyridazines8-Bromo Cyclic Adenosine MonophosphateNucleotides, CyclicAdenylate CyclaseEndopeptidasesCells, CulturedCysteine EndopeptidasesSecretory Leukocyte Peptidase InhibitorNitric OxideIsoproterenolPyrimidinonesSaquinavirTime FactorsRitonavirIndinavirHypertension, PulmonaryCysteine Proteinase InhibitorsTrypsin InhibitorsEnzyme ActivationEnoximoneProteinase Inhibitory Proteins, SecretorySerpinsNelfinavirCysteine ProteasesVinca AlkaloidsCalciumCell LineCyclic Nucleotide Phosphodiesterases, Type 2HydrolysisPenisMutationProteasome Endopeptidase ComplexSignal TransductionGuanylate CyclaseAmrinoneCyclic AMP-Dependent Protein KinasesAlprostadilNitrate Reductase (NADH)CattleEnzyme InhibitorsCyclic Nucleotide Phosphodiesterases, Type 6AminophyllineTriazinesSubstrate SpecificityProtease NexinsSilver NitrateCyclic GMP-Dependent Protein KinasesBufo bufoSulfonamidesCarbamatesRNA, MessengerRats, WistarProteolysisPhotoreceptor CellsRats, Sprague-Dawley