| | 1 | Author
| Ulrich Schraermeyer, Hennig Stieve, Michael Rack | Requires cookie* | | | Title
| Cytochemical Localization of Guanylate and Adenylate Cyclase in Photoreceptor Cells of the Fly  | | | | Abstract
| In photoreceptor cells o f invertebrates light triggers an enzyme cascade in which the phos-phoinositide pathway is crucially involved. Likewise, there is growing evidence of an impor tant role of cyclic nucleotides, too. To localize these enzymes able to catalyze the formation of cGM P and cAMP, the spatial distribution of guanylate cyclase (EC 4.6.1.2) and adenylate cyclase (EC 4.6.1.1) was determined in photoreceptor cells of the fly. In photoreceptor cells of the blowfly (Calliphora erythrocephala), the electron dense reaction product o f guanylate cyclase was found within the phototransducing region, the rhabdomeral microvilli and in the mitochondria. Staining was also observed throughout the cytoplasm of the microvilli. With the same cytochemical method, reaction product for adenylate cyclase was found on the tips of the photosensory membrane, and not in the cytoplasm o f the rhabdomeral microvilli. The results presented here further argue for an important role of one or possibly two cyclic nucleotides in the photoreceptor cells, and possibly in the process o f phototransduction of in vertebrates. | | | |
Reference
| Z. Naturforsch. 50c, 695—6 (1995); received May 24/July 10 1995 | | | |
Published
| 1995 | | | |
Keywords
| Electron Microscopy, Guanylate Cyclase, Adenylate Cyclase, Photoreceptor, Fly | | | |
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| default:Reihe_C/50/ZNC-1995-50c-0695.pdf | | | | Identifier
| ZNC-1995-50c-0695 | | | | Volume
| 50 | |
| 2 | Author
| Hans Eckstein, Heike Schlobohm | Requires cookie* | | | Title
| A Particulate Guanylate Cyclase (EC 4.6.1.2) from Growing Yeast Cells {Saccharomyces cerevisiae) | | | | Abstract
| The detection of cGMP in yeast (Eckstein 1988), but lacking hints at guanylate cyclase from sequencing of the yeast genome, raised questions about existence, isoform, and regula tion of guanylate cyclase from this organism. We found a particulate guanylate cyclase activity in yeast extracts, exhibiting properties of an integral membrane protein. Characteristics are: pH-optimum at pH 6.8, temperature-optimum around 60 °C, only slight stimulation by Mn2+. Sigmoidal enzyme kinetics indicate allosteric regulation, ATP and Ca2+ act as negative allo-steric effectors. The enzyme activity is increased by yeast alpha-1 mating factor, and by sodium nitrite, thus showing properties of particulate as well as of soluble isoforms from other eukaryotes. The activation by alpha-1 mating factor suggests receptor functions, and a role in ascospore conjugation. | | | |
Reference
| Z. Naturforsch. 52c, 373—379 (1997); received Decem ber 23 1996/February 11 1997 | | | |
Published
| 1997 | | | |
Keywords
| Guanylate Cyclase, Signal Transduction, cGMP, (Saccharomyces cerevisiae) | | | |
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| default:Reihe_C/52/ZNC-1997-52c-0373.pdf | | | | Identifier
| ZNC-1997-52c-0373 | | | | Volume
| 52 | |
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