Toxicology: Toxin Classes

toxicology

Main Animal Toxin Classes
•Cardioactive, •hemotoxins, •myotoxins, •neurotoxins, •vasoactive

Many of these toxins have other activities other than the activity listed. In addition, many toxins are found in other species as well but often in much lesser amounts.

> FIRST AID
> INGESTED TOXINS
> TOXIN CLASSES

C A R D I O A C T I V E T O X I N S
Cardiotoxins/ cytotoxins	Act on membrane lipids/proteins of blood cells or heart cells	cobras, scorpions
Digoxin-like	Cardiotonic steroids that produce severe arrythmia of heartbeat	toads

H E M O T O X I N S
Protease inhibitors	Blockage of serine proteases including plasmin, thrombin and kallikrein resulting in anticoagulant activity or hypotension	Snakes (elapids and true vipers) and certain scorpion species. Leeches contain the most powerful antithrombin toxin known
Factor X activator	Prematurely activates factor X of the blood coagulation resulting in net anticoagulation	Viper and elapid venoms
Protein C activators	Premature activation of protein C in the coagulation cascade resulting in net anticoagulation	Vipers and colubrids
Prothrombin activators	Premature activation of prothrombin in the coagulation cascade resulting in net anticoagulation	Elapid venoms
Disintegrins	Anticoagulants that bind to GPIIb/IIIa receptor on platelets	Wide spread in viper venoms and also found in leech toxins
Proteases	Myriad of actions including conversion of fibrinogen to fibrin and kallikrein like actions.	Pit-viper venoms, gila monster venoms
PLA2s	Hemorrhagic	PLA2s with a myriad of activities are scattered widely throughout venoms

M Y O T O X I N S
Myotoxins	Small proteins that facilitate the destruction of muscle cells	Pit-vipers
PLA2	Destruction of muscle cells	PLA2s with a myriad of activities are scattered widely throughout venoms
T1 and T2,	Lethal mytoxins that produce muscular contractions	Chironex fleckeri (sea wasp)

N E U R O T O X I N S
alpha-neurotoxins	Postsynaptic neurotoxins that block the acetylcholine receptor (neuromuscular)	Elapid venoms only in snakes, also found in spiders and cone snails
alpha-toxin (scorpion)	Presynaptic neurotoxins that act upon sodium channels of mammals	Scorpions
beta-toxin (scorpion)	Presynaptic neurotoxins that act upon sodium channels of mammals	Scorpions
Conatokins	inhibitiors of N-methyl-D- aspartate (NMDA) receptors resulting in an inhibition of NMDA receptor-mediated calcium influx in central nervous system neurons	Cone snails
Fasiculins	Acetylcholinesterase	Dendroaspis (mamba) species
kappa-neurotoxins	Postsynaptic neurotoxins that block the acetylcholine receptors (neuronal)	Elapid venoms only
Long and short neurotoxins	Postsynaptic neurotoxins that block the acetylcholine receptors	Elapid venoms only in snakes
mu-toxins	Directly abolish muscle action potentials through the inhibition of muscle sodium channels	spider and cone snail
omega-neurotoxins	Prevent voltage-activated entry of calcium into the nerve terminal and release of acetylcholine	cone snails and spiders
PLA2s	Presynaptic destruction of nerve cell	PLA2s are widespread in venoms
P3	High molecular weight toxins from Physalia physalis (portugese man o'war) that reversibly blocks glutamate receptors which are integral parts of the nerve conductance system	Portugues man o'war
Tetrodotoxin-like	acute respiratory failure through paralysis of the respiratory musculature with death as a result	Blue-ringed octopi, poison dart frogs, pufferfish

V A S O A C T I V E
Sarafotoxins	Vasoconstrictors	Mole vipers (Atractaspidae) only
Natriuretic peptides	Hypotensive peptides	Platypus, elapid and pit viper venoms
CrTX -I, -II, -III	Induce platelet aggregation and act as vasoconstrictors in addition to damaging the uptake/storage of noradrenaline, yet leavingthe postsynaptic contractile systems unchanged, while causing contraction of smooth muscles through the Ca2+ independent release of prostaglandins	Carybdea rastoni ("jimble")