Slow-acting hormones changes in enzyme synthesis

4 Slow-acting hormones changes in enzyme synthesis 

As discussed in section 9.1.1, there is continual turnover of proteins in the cell, and not all proteins are broken down and replaced at the same rate. Some are relatively stable, whereas others, and especially enzymes that are important in metabolic regulation, have short half-lives — of the order of minutes or hours. This rapid turnover means that it is possible to control metabolic pathways by changing the rate at which 

Slow-acting hormones, including the steroid hormones such as cortisol and the sex steroids (androgens, oestrogens and progesterone), vitamin A (section 11.2.3.2), vitamin D (section 11.3.3) and the thyroid hormones (section 11.15.3.3) act by changing the rate at which the genes for individual enzymes are expressed. 

The response is considerably slower than for hormones that increase the activity of existing enzyme molecules because of the need for an adequate amount of new enzyme protein to be synthesized. Similarly, the response is prolonged, as after the hormone has ceased to act there is still an increased amount of enzyme protein in the cell, and the effect will only diminish as the newly synthesized enzyme is catabolized. The time scale of action of slow-acting hormones ranges from hours to days. 

Binding of the activated hormone—receptor complex to the hormone response element acts as a signal to recruit the various transcription factors required for 

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