THE NATURE OF ENZYMES

[chousta]

Hi,

i have this question

"Discuss the nature of enzymes, with reference to enzyme structure as well as function."

This is my response(HAVE I MISSED ANYTHING OUT??)

Enzymes are proteins and are generally globular in shape, which is a consequence of the folding of the peptide chain. Their polypeptide chains are folded in such a way to form pockets or grooves on the surface; creating specialised regions into which the substrate molecule can "fit" into, known as the active site. The functioning of enzymes is determined by the shape of the protein.

Importantly, enzymes are protein catalysts that fascilitate the catabolism (break-down) and anabolism (synthesis) of organic compounds. Futher, enzymes allow many chemical reactions to occur within the homeostasis constraints of the living system.

Enzymes function by lowering the activation energy of reactions. By bringing the reactants closer together, chemical bonds may be weakened and reaction will proceed faster.

There are over 2000 known enzymes, each of which is involved with one specific chemical reaction. Enzymes are substrate specific.
E.g. The enzyme peptide will not work on starch (which we have experimentally shown is broken down by amalyse; as in the mouth).

As seen by the experiments in the laboratory, the activity of enzymes is strongly affected by changes in pH and temperature.

Changes in pH: alther the state of the ionisation of the charged amino acids; that play a crucial role in the substrate binding and/or the catalytic action itself. As seen experimentally, the highest reaction rate (which we want to happen in our mouths) occurs at a pH of 7. Generally, all other pHs cause the enzyme to denature, and not as effective.

Changes in temperature: speed up the rate of non-enzyme mediated reactions, as we know from reaction kinetics. However, enzymes are different, and when heated too much they becomes denatured, since they are protein dependant on their shape. When heated, hydrogen bonding and hydrophobic interactions diminish, resulting in the change of the tertiary and quarternary structure; loss of substrate affinity. The most effective temperature acccording to our experiments was 35, but according to research it is most effective at 37 (body temperature).

This all highlights the importance of enzymes and the nature of them in both the human body, and the natural environment.



THANKS!

[Darby]

Looks fine - you do have a typo in "amylase," though...

[F4T32008]

I think enzymes will not be denatured by the effects of pH..
As I know, enzymes will be denatured if it is heated about 60 degree Celcius
they are denatured because enzymes are protein itself..

[biohazard]

Extreme pH conditions (both high and low) do denature many proteins, as do several other conditions as well, in addition to high temperature (e.g. high salt concentrations). Certain enzymes tolerate extreme conditions much better than most enzymes, though. For example, there are enzymes that work perfectly well above +60 C, although not in human...

[MrMistery]

google "taq polymerase"

[Ultrashogun]

Depending on how exact your teacher is it may not be correct to say that the enzyme binds a substrate, but that it binds the substrate in distorted conformation that resembles the transition state of the reaction that is being catalyzed.

[MrMistery]

The enzyme does bind the substrate. It's just that the enzyme active site is complementary to the transition state and not the substrate. But that doesn't mean saying "enzyme binds a substrate" is wrong.

[F4T32008]

It's just that the enzyme active site is complementary to the transition state and not the substrate.

Does the enzyme really do that ?
As I know.. Both active site (enzyme and substrate) are binding together, so the can become the enzyme-substrate complex

[MrMistery]

yes, it does. You see, an enzyme with an active site complementary with the substrate would stabilize the substrate rather than promote its proceeding to the transition state. However, an enzyme with an active site complementary with the transition state can help the reaction proceed. Look up the mechanism, it's rather a lot to say...

[victor]

Yup, it does bind the substrate by making a suitable shape for the substrate (proximity & orientation effect). Then it places the nearby active groups in the substrate to the proper amino acid sidechain in the active site (strain & distortion effect). This strain n distortion of the substrate by the enzyme is also said as the transition state of the substrate, because in this state the substrate can be easily changed due to its instability. After that, the enzyme can easily alter the substrate into product either by covalent catalysis or by acid-base changes.