Posted by Larry Hoover on August 7, 2003, at 8:10:03
In reply to Irreversible Maoi??, posted by makaveli on August 7, 2003, at 7:18:23
> I was curiuos what this meant by "irreversible"???
It means the enzyme bound to the MAOI is permanently destroyed, rather than temporarily inactivated.
Let me use an analogy. Enzymes have active sites with a very specific three-dimensional form. Only molecules with particular structures (called substrates) can fit the active site. Because of this structural specificity on both sides of the interaction, a common analogy is like a lock and a key. Only certain keys (substrates) can enter the lock (enzyme).
Inhibition of an enzyme can be accomplished in a number of ways. A competitive inhibitor fits the enzyme active site, but doesn't do anything while there. It just occupies the enzyme for a while, reducing the ability of normal substrates to access the active site. In the lock and key model, that's like putting the wrong key in the lock, and leaving it there for a while. An example of such an inhibitor of MAO is moclobemide (Manerix, Aurorix). It is said to be reversible, because once it leaves the active site, the enzyme resumes its normal function, acting on substrates.
An irreversible inhibitor either doesn't ever leave the active site, or, it may damage the enzyme in such a way that the active site loses its activity. Going back to the lock and key model, that might be like putting crazy glue in the key channel.
Your body makes MAO every day. Each MAO molecule has a lifespan of about two weeks. Every day that you take an irreversible MAOI, you damage or destroy a good proportion of the available MAO enzyme molecules. But your body makes more all the time (and may, conceivably, increase the rate of production because of all the destruction going on), so you have to take the inhibitor every day, as well (your kidneys and liver get rid of the MAOI all the time, too).
It's a dynamic system, with constant inputs and outputs. It's not static, like you wipe out all the MAO and then it's over.
Lar
poster:Larry Hoover
thread:248864
URL: http://www.dr-bob.org/babble/20030807/msgs/248887.html