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Sunday, January 13, 2013

Enzymes


The purpose of this post is to explain how our bodies produce the enzymes that are crucial in ‘enabling’ the chemical reactions that have to happen in our cells for us to function. Understanding how our cells make enzymes may not be your ‘cup of tea’ but to me it’s a fascinating tale and it’s told here to show that any advertisement that professes to improve your health by suggesting you take enzyme supplements is not to be believed.  Enzymes are proteins and your digestive system breaks them down like it would any other protein food like meat or eggs. There is one exception - for those who can’t digest milk, lactase enzyme can be taken along with dairy products.

The diagram above shows just what happens in a cell when it signals its nucleus that it needs a particular enzyme. [If ever you want to enlarge a diagram like the one above, click on it and choose x-large from the menu.] Starting at the top, a section of DNA unzips where the gene that has the instructions to make that enzyme is found, An mRNA molecule copies the sequence code, the DNA zips up again and the mRNA leaves the nucleus. The cell fluid should contain all the 20 types of amino acids and they are attracted to sites on the mRNA which in turn joins them up in the right order to make the long string enzyme protein the cell needs.
The purpose of the enzyme is shown in the diagram on the right and if you click on a simple video you will see an animated version of how it works. For reasons I'll explain below, each long string of amino acids folds up in a very specific way to create a shape on its surface that a molecule fits into - like a key in a lock.  As the molecule [or molecules] in the cell sits on the enzyme, there are interactions with it that makes a desired chemical reaction occur quickly and the product[s] leave the site so the enzyme is free to act again. When enough of the product has formed, the enzyme can be turned off by binding with competing molecules as shown in this video
When the mRNA is stringing together the many thousands of amino acids to make an enzyme, they're all in a line but as they hit the watery fluid in the cell, they very quickly start to fold up into an exact desired shape. The details of how this happens still puzzles scientists but there are some interesting clues. Each of the amino acids has its own properties. Some have electric charges that want to be near other charges like those in water molecules in the cell. Others have side chains that are repelled by water, like oil and water don't mix, so they have a tendency to sequester themselves on the inside of the molecule. Still others make special bridge connections. The diagram on the left gives an idea of the complexity of the folding of an enzyme molecule. Enlarging the diagram show gives you a new respect for chemists who can work out the structure of these giant molecules!! 
Our DNA has around 25,000 genes altogether and most of them code for making a specific type of enzyme protein. It is easy to understand that to stay healthy, we need to have all the amino acids available in our cells to produce enzymes. So the bottom line is: 
- be sure you are getting the proteins you need in your diet  [A couple of weeks ago I was extolling the virtues of quinoa because it is a grain that when cooked, provides all the amino acids that are needed] 
- forget about buying expensive enzyme supplements - except of course for 'lactase' if you need itRie

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