Drug targets intracellular enzymes

The main drug targets are enzymes and receptors that are found on the cell surface or reside within the intracellular matrix. 

The main drug targets are enzymes, intracellular receptors, and extracellular (cell surface) receptors. Drugs are normally designed to interact with these entities either as agonists or antagonists to achieve control over the disease pathway. 

More recently, research indicates that the anthracycline compounds have an inhibitory effect on the intracellular enzyme topoisomerase II (also see Chapter 7). This has been taken as evidence that this enzyme may be the primary target for these drugs. A more balanced view at this time may be that the carcinolytic mechanism of action of the anthracycline antibiotics is related to the binding affinity to DNA (intercalation), inhibition of nucleic acid synthesis, and topoisomerase II interactions. 

There are a variety of structural classes of compounds that are active against each phosphodiesterase, and evidence suggests that selective inhibitors of PDEs can be identified. The structural diversity of PDE inhibitors provides a multitude of opportunities for development of compounds with drug-like properties. Furthermore, phosphodiesterase inhibition, which avoids direct interaction of a compound with a cell surface or nuclear receptor, may circumvent some of the target selectivity issues that can complicate receptor-based therapeutic approaches. As noted above, the specific subcellular distribution of phosphodiesterase enzymes is a key feature of their ability to modulate intracellular signaling pathways. This localization of the enzyme may minimize non-specific target... 

Mechanisms of drug action. To mediate a response the drug can bind to the desired therapeutic target or to other molecular targets such as G-protein-coupled receptors (GPCRs), ion channels, or transporters on the cell membrane, or to intracellular targets such as enzymes and nuclear hormone receptors. 

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