What Is It That Holds the Enzyme Substrate Complex Together?

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Enzymes are very specialized proteins that catalyze specific chemical reactions in the cell. Find out what it is that holds the enzyme substrate complex together with help from an experienced chemistry professional in this free video clip.

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Hi. I'm Dan Weisenberger and this is "What Is It That Holds the Enzyme Substrate Complex Together?" Well, enzymes, to review, are very specialized proteins that catalyze specific chemical reactions in the cell. And, they do so by bringing substrates and cofactors and things necessary for the reaction into a small pocket of the enzyme, known as its active site, to efficiently perform a chemical reaction. Now, there are several interactions that occur at the active site during catalysis. Some of them are non-covalent interactions between the enzyme active site amino acids and the substrate. These involve the binding of ions, typically, metals, things like magnesium ions that are essential for coordinating the enzyme substrate complex, van der Waals forces, these are small shifts in polarity between molecules that could make some molecules attracted more to others. And, finally, hydrogen bonding, which is exemplified in water, by which the oxygens of one water molecule and the hydrogens of another water molecule are pulled together by non-covalent bonds and this is one of the main reasons why water is the liquid that it is. And, secondly, there are covalent interactions between the enzyme and its substrate, although these are very transient. And, I'll give one example of the enzymes that catalyze DNA methylation in mammalian cells, these are DNA methyl transferases. And, they catalyze the addition of a methyl group on to the C5 position of carbon, shown here. So, how does this happen? Well, in this situation, the enzyme, together with the substrate, which is a methyl group linked to a large cofactor called exomethylenes, get together and the enzyme actually finds a - binds, temporarily, to the cytosine residue of DNA and, at that point, the electrons here can grab that methyl group, bind to it and, then, release the enzyme for it to do other catalysis throughout the cell. I'm Dan Weisenberger and this is "What s It That Holds the Enzyme Substrate Complex Together?"

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