text: A 46-amino acid segment in phosphodiesterase-5 GAF-B domain provides for high vardenafil potency over sildenafil and tadalafil and is involved in phosphodiesterase-5 dimerization.
  Phosphodiesterase-5 (PDE5) contains a catalytic domain (C domain) that hydrolyzes cGMP and a regulatory domain (R domain) that contains two mammalian cGMP-binding phosphodiesterase, Anabaena adenylyl cyclases, Escherichia coli FhlAs (GAFs) (A and B) and a phosphorylation site for cyclic nucleotide-dependent protein kinases (cNPKs). Binding of cGMP to GAF-A increases cNPK phosphorylation of PDE5 and improves catalytic site affinity for cGMP or inhibitors. GAF-B contributes to dimerization of PDE5, inhibition of cGMP binding to GAF-A, and sequestration of the phosphorylation site. To probe potential PDE5 R domain effects on catalytic site affinity for certain inhibitors, four N-terminal truncation mutants were generated: PDE5Delta1-321 contained GAF-B domain, C domain, and the sequence between GAF-A and -B; PDE5Delta1-419 contained GAF-B and C domain; PDE5Delta1-465 contained the C domain and the C-terminal portion of GAF-B; and PDE5Delta1-534 contained only C domain. Truncated proteins with a complete GAF-B were dimers, but those lacking the N-terminal 46 amino acids of GAF-B were monomers, indicating that these residues are vital for GAF-B-mediated PDE5 dimerization. K(m) values of the mutants for cGMP were similar to that of full-length PDE5. All PDE5 constructs had similar affinities for 3-isobutyl-1-methylxanthine, sildenafil, tadalafil, and UK-122764, but mutants containing a complete GAF-B had 7- to 18-fold higher affinity for vardenafil-based compounds compared with those lacking a complete GAF-B. This indicated that the N-terminal 46 amino acids in GAF-B are required for high vardenafil potency. This is the first evidence that PDE5 R domain, and GAF-B in particular, influences affinity and selectivity of the catalytic site for certain classes of inhibitors.
entities.id: T10 T11 T12 T13 T14 T15 T16 T17 T18 T19 T1 T20 T21 T22 T23 T24 T25 T26 T27 T28 T29 T2 T30 T31 T32 T33 T34 T35 T36 T37 T38 T39 T3 T40 T41 T42 T43 T44 T45 T46 T47 T48 T49 T4 T50 T51 T52 T53 T54 T55 T56 T57 T58 T59 T5 T60 T61 T6 T7 T8 T9
entities.type: CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL GENE-Y GENE-N GENE-N GENE-N GENE-Y CHEMICAL GENE-Y GENE-Y GENE-N GENE-N GENE-N GENE-N GENE-N GENE-N GENE-Y GENE-Y CHEMICAL GENE-Y GENE-N GENE-N GENE-N GENE-N GENE-N GENE-Y GENE-N GENE-Y GENE-N CHEMICAL GENE-N GENE-Y GENE-N GENE-N GENE-Y GENE-N GENE-Y GENE-N GENE-Y GENE-Y CHEMICAL GENE-Y GENE-N CHEMICAL CHEMICAL CHEMICAL CHEMICAL
entities.text: N amino acids vardenafil adenylyl cyclic nucleotide cGMP cGMP cGMP N cGMP N C sildenafil tadalafil amino acid vardenafil Phosphodiesterase-5 GAF-B GAF-B GAF-B PDE5 amino acids PDE5 PDE5 mammalian cGMP-binding phosphodiesterase GAF-B GAF-B GAF-B PDE5 R domain GAF-B Anabaena adenylyl cyclases Escherichia coli FhlAs cGMP PDE5 (GAFs) (A and B) cyclic nucleotide-dependent protein kinases cNPKs GAF-A cNPK PDE5 GAF-B PDE5 GAF-A 3-isobutyl-1-methylxanthine PDE5 R domain PDE5Delta1-321 GAF-B domain GAF-A and -B PDE5Delta1-419 GAF-B and C domain PDE5Delta1-465 GAF-B PDE5Delta1-534 phosphodiesterase-5 sildenafil phosphodiesterase-5 GAF-B domain tadalafil UK-122764 vardenafil cGMP