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zymogens vs. pro-proteins?

Discussion in 'MCAT Study Question Q&A' started by ssnickerer, May 7, 2008.

  1. ssnickerer

    ssnickerer A Thinker 10+ Year Member

    Jul 4, 2007
    Duke University
    Proteins that end in "-ogen" are zymogens, and proteins that start with "pro-" are what I call pro-proteins... (is there a more technical term?).

    Examples: pepsinogen/fibrinogen vs. prothrombin

    Anyway, what is the difference between how these two protein precursors work? From what I've been reading, it seems that they both are cleaved to release the active form of the protein. But there must be something different, right? Otherwise, why the different nomenclature, if not to confuse people with synonyms?

    EDIT: Isn't there also a distinction between "pre-" and "pro-"?
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  3. JA Prufrock

    JA Prufrock Serenity Now! 2+ Year Member

    Mar 31, 2008
    The context in which that I learned about the two was different. Zymogens were mentioned when discussing enzymes, whereas pro-proteins referred to hormone precursors. I don't know if there's any other relevant difference. I don't know if there is a difference between "pre" and "pro," though I do know that peptide hormones undergo a couple major processing steps. After translation, when they still have the 'signal sequence' attached, they are called pre-prohormones. After that sequence is cleaved they are called pro-hormones.
  4. LoveMyRam

    LoveMyRam 7+ Year Member

    Sep 24, 2006
    Zymogens are inactive enzymes that are usually cleaved or modified to render an active enzyme. Zymogen is merely a term to refer to the "pro-form" or the inactive precursor.

    A pro protein or pro peptide is a precursor to a protein or peptide that exists with in the cell before it is secreted. Therefore it usually occurs that a protein is translated into its proform in the Rough Endoplasmic Reticulum and then secreted outside of the cell where it is then cleaved under certain conditions. This is for the purpose of preventing over activity of the protein or in some cases to prevent activity of the protein with in the cell.
    One case that comes to mind is the release of procollagen from the cell to form collagen in the extracellular matrix. Because of the tensile strength of polymers making the collagen unit, if this occured within the cell it would not be able to successfully be teansported out of the cell.

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