The specificity of yeast low-Km cyclic AMP phosphodiesterase towards free bivalent metal ions and the diastereoisomers of cyclic adenosine phosphorothioate

Abstract

The relative activity of a zinc-containing cyclic AMP phosphodiesterase towards the (Sp)- compared with the (Rp)-diastereoisomer of cyclic adensine phosphorothioate varied with the identity of the free bivalent metal ion from more than 35 to 0.074 along the series Mg2+ greater than Mn2+ greater than Co2+ greater than Zn2+ greater than Cd2+, showing that this ion, and not the tightly bound zinc, bonds to the phosphorothioate moiety of the substrate.

Cloning and characterization of the high-affinity cAMP phosphodiesterase of Saccharomyces cerevisiae.

“…The Lineweaver-Burk plot of these data (Fig. 4) indicates a Km of 1.0 x 10-6 M, in good agreement with the data of Suoranta and Londesborough (26), who analyzed the high-affinity cAMP PDEase of yeast.…”

“…Two cAMP PDEase activities have been described in yeast: a low-affinity form having broad specificity and a high-affinity form having narrow specificity (25,26). The high-affinity form is a zinc-requiring enzyme, with a Km for cAMP of 1 x 10-6 M, and fails to hydrolyze cGMP (26). It has an amino acid composition similar to that which we predict for the PDE2-encoded product.…”

“…might encode a cAMP PDEase. Biochemical analysis had previously indicated that there are at least two cAMP PDEases in yeast, one with low affinity and broad specificity and one with high affinity and narrow specificity (25,26). The amino acid compositions of these enzymes have been published.…”

“…Overexpression of the cAMP effector pathway because of high level expression of adenylate cyclase (7), or because of overexpression of the catalytic subunit of cAMP-dependent protein kinase (our unpublished data), or because of deletion of the regulatory subunit of cAMP-dependent protein kinase leads to the same set of phenotypes as the RAS2Vall9 mutation (7,27 (28,29). Two cAMP PDEase activities have been described in yeast: a low-affinity form having broad specificity and a high-affinity form having narrow specificity (25,26). The high-affinity form is a zinc-requiring enzyme, with a Km for cAMP of 1 x 10-6 M, and fails to hydrolyze cGMP (26).…”

Identification of a conserved domain among cyclic nucleotide phosphodiesterases from diverse species.

“…The Km values of the cGMPstimulated and the Cam-dependent PDEases for both cGMP and cAMP are in the 10-30 ,uM range while those for the cGMP-inhibited PDEase are submicromolar. Most of the mammalian isozymes can hydrolyze both cAMP and cGMP, albeit at different rates; however the Drosophila dunce' (dnc+) gene product (9,10) and the yeast PDE2 gene product (11,12) compared in this report have a distinct substrate preference for cAMP (Table 1).…”