Characterization of guanylate cyclase in squid photoreceptors.

Academic Article


  • Light causes a rapid, 1.7-fold increase in cyclic GMP concentration in intact squid retinas (Johnson et al. (1986]. To determine whether light-induced changes in cyclic GMP concentration result from activation of guanylate cyclase, we have studied the regulation of guanylate cyclase activity in squid (Loligo pealei) photoreceptors. The enzyme is membrane-associated and activity is enhanced by the detergents Triton X-100 or digitonin. The enzyme requires divalent cations, Mn2+ being preferred over Mg2+. The dependence of enzyme activity on the MnGTP concentration deviates from simple Michaelis-Menten kinetics. Under conditions where a light-induced binding of GTP to the guanine nucleotide regulatory protein can be observed, no light-induced change in guanylate cyclase could be detected.
  • Authors

  • Robinson, PR
  • Cote, Rick
  • Status

    Publication Date

  • July 1989
  • Published In


  • Animals
  • Cell Membrane
  • Decapodiformes
  • Detergents
  • Enzyme Activation
  • GTP-Binding Proteins
  • Guanylate Cyclase
  • Light
  • Magnesium
  • Manganese
  • Photoreceptor Cells
  • Rhodopsin
  • Digital Object Identifier (doi)

    Pubmed Id

  • 2577264
  • Start Page

  • 1
  • End Page

  • 7
  • Volume

  • 3
  • Issue

  • 1