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Thread: Formation of an enzyme and its active site?

  1. #1 Formation of an enzyme and its active site? 
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    At what point during the formation of an enzyme does its active site start to physically form?

    Is there in fact a general answer to this question, or is it too obscure? Would the point in which the active site starts to form vary for each type of enzyme?

    As far as I understand it there are 4 main stages to the formation of a protein (e.g. an enzyme):

    The formation of the polypeptide chain/s - where condensation reactions occur between amino acid monomers, causing them to bond together (in peptide bonds) in a certain sequence and form one or more polypeptide chains (polymerisation). These polypeptide chains form the primary structure of a protein.

    The formation of the secondary structure - Weak hydrogen bonds form between positively charged hydrogen atoms and negatively charged oxygen atoms on either side of the peptide bonds of the linked amino acids in the polypeptide chains. These hydrogen bonds cause the polypeptide chain/s to twist into a 3D structure (such as an a-helix).

    The formation of the tertiary structure: Disulfide, ionic and more hydrogen bonds occur between amino acids, forming a more unique and complex shape.

    The formation of the quaternary structure: Prosthetic groups bond to the tertiary structure and increase the complexity of the shape of the protein.


    (I'd be really appreciative if someone could correct me if I've made any mistakes or left anything important out of the above.)

    What I'm wondering is: at what point during the formation of an enzyme protein does the active site physically start to form?
    Is it when the hydrogen bonds occur during the formation of the secondary protein structure, as this is the first stage that it starts take on a shape? (Or at this stage is the shape too primitive to show an active site?) Does the active site start to form during the formation of the secondary structure and then build up more as the tertiary and quaternary structures are then formed?
    Or conversely, does the active site begin forming during the tertiary or quaternary stages?

    I've read in a book that states that changing an amino acid of an enzyme, that is of a different part of the enzyme to the active site, prevents the enzyme from functioning because it affects the formation of the tertiary structure which, in turn, changes the shape of the active site. This has something specifically to do with the hydrogen bonds of the enzyme. Does this mean that it is the hydrogen bonds of the secondary structure breaking that is so damaging to the formation of the enzyme, as it is these bonds that initially lay a foundation for the tertiary and quaternary structures of the enzyme to form?

    I really apologize if this post makes no sense. I'm new to biology and am having a lot of trouble understanding things and phrasing myself! I hope you can bear with me!

    I'd be very grateful for any help you can offer.

    Thank you!


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  3. #2 Re: Formation of an enzyme and its active site? 
    Forum Professor jrmonroe's Avatar
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    Quote Originally Posted by emetzner
    At what point during the formation of an enzyme does its active site start to physically form?

    The formation of the tertiary structure: Disulfide, ionic and more hydrogen bonds occur between amino acids, forming a more unique and complex shape.
    You've had the answer to your own question all along (underlined above). Make sense? Plus, many/most enzymes don't form quaternary structures. Forming its tertiary structure is the final stage for most enzymes.

    The primary structure is a simple string of amino acids (ie, a polypeptide) coming out of a ribosome. The secondary structure begins the folding process, but is incomplete.

    In addition to this, I'm pretty sure modifications (deletions, insertions, splices etc) to amino acids can occur, and I'm pretty sure they can occur after the primary structure forms.


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