Isopimaric acid
Encyclopedia
Isopimaric acid is a toxin
which acts as a large conductance Ca2+-activated K+ channel (BK channel
) opener.
group which is a tricyclic diterpene. It has a condensed three-ring structure, one carboxyl-group and a (conjugated) double bond.
).
(CTX). Opening of the BK channel leads to an increased K+-efflux which hyperpolarizes the resting membrane potential, reducing the excitability of the cell in which the BK-channel is expressed.
hepatocytes have shown that IPA increases intracellular calcium
release, leading to a disturbance in the calcium homeostasis. This could be important in the possible toxicity of the toxin.
Toxin
A toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...
which acts as a large conductance Ca2+-activated K+ channel (BK channel
BK channel
BK channels , also called Maxi-K or slo1, are ion channels characterized by their large conductance of potassium ions through cell membranes. These channels are activated by changes in membrane electrical potential and/or by increases in concentration of intracellular calcium ion...
) opener.
Chemistry
IPA is one of the members of the resin acidResin acid
Resin acids usually refers to mixtures primarily. Abietic acid is the main component but several related carboxylic acids. Nearly all resin acids have the same basic skeleton: three fused ring fused with the empirical formula C19H29COOH. These materials occur in rosin but also occur in fossil...
group which is a tricyclic diterpene. It has a condensed three-ring structure, one carboxyl-group and a (conjugated) double bond.
Target
IPA acts on the large-conductance calcium activated K+ channels ( BK channelsBK channel
BK channels , also called Maxi-K or slo1, are ion channels characterized by their large conductance of potassium ions through cell membranes. These channels are activated by changes in membrane electrical potential and/or by increases in concentration of intracellular calcium ion...
).
Mode of action
BK channels are formed by α subunits and accessory β subunits arranged in tetramers. The α subunit forms the ion conduction pore and the β subunit contributes to channel gating. IPA interaction with the BK channel enhances Ca2+ and / or voltage sensitivity of the α subunit of BK channels without affecting the channel conductance. In this state BK channels can still be inhibited by one of their inhibitors, like charybdotoxinCharybdotoxin
Charybdotoxin is a 37 amino acid neurotoxin from the venom of the scorpion Leiurus quinquestriatus hebraeus that blocks calcium-activated potassium channels. This blockade causes hyperexcitability of the nervous system.-Chemical properties:...
(CTX). Opening of the BK channel leads to an increased K+-efflux which hyperpolarizes the resting membrane potential, reducing the excitability of the cell in which the BK-channel is expressed.
Toxicity
Studies on rainbow troutTrout
Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...
hepatocytes have shown that IPA increases intracellular calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
release, leading to a disturbance in the calcium homeostasis. This could be important in the possible toxicity of the toxin.