How do toxins interact with biological targets?

Toxins are the poisonous or toxic substances that are generated by metabolic activities in the living organisms and can pose a threat to human lives. Some drugs may contain toxins in small amounts but can be fatal or harmful if present in larger amounts. They can be naturally occurring organic small molecules or conjugated proteins, peptides that can be absorbed by the body tissues thereby interacting with biological macromolecules such as enzymes or cellular receptors.

The mechanism of action of toxin is by binding on to the host cell surface inducing translocation across the plasma membrane by undergoing endocytosis where they penetrate the endosomal membrane to reach the cytosol.

The interaction of the toxicants with the biological target is done through malfunctioning of the target such as disruption of the protein structure rendering them inactive resulting in disruption of membrane protein channels. This can induce the effect of transmembrane signaling and loss of enzyme function.

The toxicology studies involve the study of the toxins and its action in the human body system. The toxin generated chooses different translocation pathways for delivering the macromolecules to cytosol to propagate their function. For the therapeutic application understanding these routes is essential for the development of anti-toxin treatments or for the discovery of drugs based on toxin eliminations. By studying the toxin route the particular cell can be specifically targeted. A wide range of therapeutic research is conducted where the toxins are destroyed before reaching the site of action and aiding in the therapeutic development in the cancer antiviral, antibacterial research.

The toxin and the toxicants can enter the body through different means such as skin penetration, inhalation, or ingestion. Toxicology studies provide information on different terminologies used according to their site where they show prominent action. Genitotoxin, hemotoxin and hepatotoxin are few examples of the toxins that can affect the body at different places according to their mode of action at respective sites and can induce harmful effects in the human body system.

Toxins are categorized into endotoxins and exotoxins. Exotoxins are excreted by an organism whereas endotoxins are released when the bacteria are lysed.

Toxicity is highly responsible for the attrition rates of the drug candidates and can result in higher estimates and costs for the drug development process particularly when it is not recognized until the clinical trials or post marketing. The toxicity is induced due to several reasons. It can be due to mechanism based production, immune hypersensitivity or due to bio-activation modification. Hence the drug toxicology studies form an integral part of the drug development process.

Toxico-dynamics is the branch of toxicology that gives us information about how the compound interacts with its biological target giving rise to adverse effects. The biomolecular targets involved are generally protein, DNA, RNA or even smaller molecules that interact with the toxicant leading to adverse effects. The target protein can be either receptor, enzymatic and transporter type and depending upon those corresponding protein interactions take place. 

Enzyme activity is exercised through the binding action where the compound binds to an enzyme either non covalently or covalently. Non covalent binding induces a reversible inhibition whereas the covalent binding induces irreversible inhibition.