Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.6.1.2 (guanylate cyclase)
 8,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tryptic bovine brain calmodulin fragments 1-77 or 1-106 reactivated La-inactivated ciliary guanylate cyclase from Paramecium dose-dependently up to 60%. They were 20-fold less potent compared to bovine brain calmodulin. Fragment 78-148 was even less active. Concomitant addition of fragments 1-77 and 78-148 had no additive effect. Genetically engineered calmodulin lacking a blocked amino terminus and trimethyllysine at position 115 reactivated La-treated guanylate cyclase as good as bovine brain calmodulin. After detergent solubilization of La-inactivated guanylate cyclase intact bovine brain calmodulin and calmodulin fragments 1-77 and 78-148 were equipotent. 80% Reactivation was obtained with 40 microM of either fragment.
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PMID:Effect of tryptic calmodulin fragments on guanylate cyclase activity from Paramecium tetraurelia. 288 41

Ca2+-regulated guanylate cyclase in ciliary membranes from Paramecium contained tightly bound calmodulin. Antisera against calmodulin from Tetrahymena and soybean inhibited enzyme activity. EGTA did not easily release calmodulin; however, La3+ inhibited guanylate cyclase by dissociation of calmodulin. While La could not replace Ca in the activation of guanylate cyclase, it substituted for Ca2+ in the activation of calmodulin-dependent phosphodiesterase from pig brain independently of whether homologous or Paramecium calmodulin was used. After removal of endogenous calmodulin from guanylate cyclase, reconstitution was achieved with calmodulin from Paramecium, Tetrahymena, pig brain, and soybean. Ca2+-binding proteins lacking trimethyllysine like calmodulin from Dictyostelium, parvalbumin, and troponin C failed to restore enzyme activity. The properties of the native and reconstituted guanylate cyclase/calmodulin complex were compared. Reassociation of calmodulin with its target enzyme was weak since all calmodulin remained in the supernatant after a single centrifugation. While most enzyme characteristics remained unchanged in the reconstituted complex, the inhibition by Ca greater than 100 microM was of a mixed-type compared to noncompetitive inhibition in the native enzyme. The regulation of the enzyme by cations was also altered. Whereas Ca was the most potent and specific activator of the native enzyme, in the reconstituted system Sr was far more effective.
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PMID:Calcium/calmodulin-regulated guanylate cyclase of the excitable ciliary membrane from Paramecium. Dissociation of calmodulin by La3+: calmodulin specificity and properties of the reconstituted guanylate cyclase. 613 52

A guanylate cyclase of high specific activity was localized in the ciliary membrane from Tetrahymena pyriformis. Purity of cilia was checked by electron microscopy and purity of membrane fractions isolated by a sucrose density gradient by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. Enzyme activity was due to the presence of endogenous calmodulin as evidenced by the inhibition of guanylate cyclase by addition of antiserum against calmodulin from Tetrahymena or soybean. Removal of endogenous calmodulin by La3+-treatment of ciliary membranes resulted in loss of guanylate cyclase activity. In addition to protozoan calmodulins, the original activity could also be restored by the nonhomologous calmodulins from soybean and pig brain but not by calcium-binding proteins like Dictyostelium calmodulin, parvalbumin, and troponin C, lacking the trimethyllysine characteristic for mammalian calmodulins. However, only calmodulins from the protozoans Tetrahymena and Paramecium stimulated guanylate cyclase activity in excess of the initial activity. This indicates that the guanylate cyclase either contains two binding sites for calmodulin with different specificities or that a single, but only partially occupied binding site is modified possibly by hydrolytic exo-proteases during membrane preparation. The ciliary membrane from Tetrahymena contains a discrete calcium-permeability as demonstrated by calcium-flux measurements using the calcium indicator dye arsenazo III. In analogy to the excitable ciliary membrane of the larger relative Paramecium, the ciliary membrane of Tetrahymena may thus carry the voltage-sensitive calcium-channels known from electrophysiological studies.
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PMID:Calcium/calmodulin-regulated guanylate cyclase and calcium-permeability in the ciliary membrane from Tetrahymena. 614 Jan 65