The Interaction of Cations with Activity of Soluble Protein Kinase C from Mouse Brain

Publisher Website
Google Scholar
Abstract
The interaction of some cations with the enzymatic activity of soluble protein kinase C was determined in order to elucidate whether protein kinase C can be activated by other metal cations besides Ca2+. Protein kinase C was activated by Ca2+and Sr2+having EC50 values of nearly 10 μM and 200 μM, respectively. Ba2+likewise activated protein kinase C but was less potent. Co2+, Ni2+and Mn2+had no activating effects on the activity in the absence of Ca2+, but was slightly reduced in the presence of Ca2+(0.5 mM). Cations with ionic radii close to Ca2+(0.99 Å) inhibited the activity irrespective of the absence or presence of Ca2+. The order of potency is as follows: Hg2+> Cd2+∼ Cu2+≫ Sm3+> Tb3+> La3+, Pb2+and Zn2+, which showed a high affinity to SH‐groups, as well as Hg2+, Cd2+and Cu2+, which also inhibited the activity. Thus, among the ions investigated, the alkaline‐earth ions Sr2+and Ba2+could be substituted for Ca2+, irrespective of ionic radii. The serious environmental pollutants such as Hg2+, Cd2+or Pb2+impaired the activity of protein kinase C probably due to SH‐blocking.