Enzymes as targets for therapy

In theory, it shonld be possible to alleviate the symptoms of an enzyme dehciency by administering the missing enzyme bnt this is made difficult becanse enzymes do not cross membranes and so fail to enter cells and they also indnce an immnne response. A solution is the nse of liposomes - small lipoprotein vesicles in which enzymes are entrapped so that they fuse with the plasma membrane in vivo and introdnce the enzymes into the cell. The liposome protects the introdnced enzyme from both the host s immnne system and from degradative enzymes. This approach has been used particularly in the treatment for deficiencies of enzymes in the lysosomes. 

Five examples of diseases that are inflnenced by drags that inhibit enzymes are presented depression, hypertension, bacterial infections, viral infections (retrovirnses) and cancer. 

This condition is cansed by a deficiency of one or more of the monoamine nenrotransmitters in the brain (e.g. noradrenaline, dopamine, 5-hydroxytryptamine). One means of increasing the concentration of the neurotransmitters is to inhibit one of the enzymes that degrade the neurotransmitter in the brain. For the monoamines, a key degradative enzyme is monoamine oxidase, which catalyses the reaction 

Drags that inhibit this enzyme result in an increase in the concentration of the monoamines and this can alleviate the depression, at least in some patients (Chapter 14). 

The cause of this disease is not known, but one factor that increases blood pressure is a plasma protein, angiotensin-II, which is produced via an enzyme cascade in blood, as follows  

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