Receptor enzyme-linked

Tyrosine kinase receptors are important enzyme-linked receptors... 

There are five known classes of enzyme-linked receptors (1) receptor tyrosine kinases, which phosphorylate specific tyrosine residues on intracellular signaling proteins (2) tyrosine kinase-associated receptors, such as the prolactin and growth hormone receptors we have already discussed, which... 

There are basically two different enzyme activities that can be stimulated in enzyme-linked receptors. A receptor tyrosine kinase recognizes one or more specific tyrosines in the target and uses ATP to phosphorylate it. Often part of the activation involves the receptor phosphoryla-... 

Guanylate cyclase signaling pathway also utilizes an enzyme-linked receptor model. The effector enzyme, guanylate cyclase, converts GTP to cGMP, which in turn activates cGMP dependent protein kinase or phosphodiesterases. 

Fig. 2. Signal transduction through an enzyme-linked receptor such as the insulin receptor.

Figure 19.2. Schematic representation of some receptor superfamilies. This figure represents the common mechanisms of the four major receptor families discussed in Section 19.2. Example 1 is of the G protein-coupled receptor. Example 2 represents the ionotropic receptor (ligand-gated ion channel) superfamily, on which multiple binding sites are known to exist (see Figure 19.1). Example 3 represents the steroid receptor superfamily. Example 4 depicts the enzyme-linked receptor superfamily.

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