ISSN:
1550-7408
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
SYNOPSIS. Cyclic nucleotide phosphodiesterase [EC 3.1.4.17] was examined in Tetrahymena pyriformis strain NT-1. Enzymic activity was associated with the soluble and the particulate fractions, whereas most of the cyclic GMP phosphodiesterase activity was localized in the soluble fraction: the activities were optimal at pH 8.0–9.0. Although very low activities were detected in the absence of divalent cations, they were significantly increased by the addition of either Mg2+ or Mn2-. A kinetic analysis of the properties of the enzymes yielded 2 apparent KIII values ranging in concentration from 0.5 to 50 μM and from 0.1 to 62 μ M for cyclic AMP and GMP. respectively. A Ca2+-dependent activating factor for cyclic nucleotide phosphodiesterase was extracted from Tetrahymena cells, but this factor did not stimulate guanylate cyclase [EC 4.6.1.2] activity in this organism. On the other hand, Tetrahymena also contained a protein activator which stimulated guanylate cyclase in the presence of Ca2+, although this activator did not stimulate the phosphodiesterase. the results suggested that Tetrahymena might contain 2 types of Ca2+-dependent activators, one specific for phosphodiesterase and the other for guanylate cyclase.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1550-7408.1980.tb04275.x
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