Enzymes

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    • #16734
      rk386
      Participant

      Do enzymes in the body last permanently, or do they over time get broken down and then replenished/rebuilt/replaced? Also, what controls the amount of enzyme present?

    • #112042
      jonmoulton
      Participant

      Enzymes are degraded over time. Some are relatively short-lived while others are very persistent, but damage accumulates and they are eventually broken down.

      This page might help the system make more sense.

      http://en.wikipedia.org/wiki/Proteolysis

    • #112043
      david23
      Participant

      what controls the enzyme levels? your genes, and hormonal regulations which again your genes

    • #112045
      JackBean
      Participant

      you seem to put everything under genes, but genes are controlled by many factors as well

    • #112053
      rk386
      Participant

      Thanks. Follow-up question:

      Enzymes are degraded over time. Some are relatively short-lived while others are very persistent, but damage accumulates and they are eventually broken down.

      Is it known which types of enzymes break down quickly and which are persistent?

    • #112054
      JackBean
      Participant

      Yes, there are soe well-known examples. For those you don’t know about, you can make some predictions.

    • #112057
      rk386
      Participant

      Thanks. If I wanted to look more into this, where would I look?

    • #112058
      JackBean
      Participant

      The first choice should be Alberts’ The Cell

    • #112059
      rk386
      Participant

      Oh, great, I have that.

    • #112062
      jonmoulton
      Participant

      Look for "protein turnover". Here’s an introduction. http://en.wikipedia.org/wiki/Protein_turnover

    • #112095
      rk386
      Participant

      Thanks. Have studies on protein turnover been done for specific proteins, or is it just known in general that that is what happens?

    • #112096
      jonmoulton
      Participant

      It has been done for many specific proteins. One good method is pulse-chase analysis. http://en.wikipedia.org/wiki/Pulse-chase_analysis

    • #112097
      rk386
      Participant

      Thanks. It is pretty amazing what technology can do. So by this method, the rate at which a protein breaks down can be determined, e.g. an enzyme?

    • #112098
      jonmoulton
      Participant

      Yes.

    • #112108
      KileYe
      Participant

      They will degrade through metabolism

    • #112118
      rk386
      Participant

      What controls that metabolism?

    • #112120
      rk386
      Participant

      Also, in terms of the rate at which an enzyme acts, other than substrate concentration and reaction rate, are there any other conditions that would regulate the rate at which an enzyme works? Are there such thing as inherently "slower" or "faster" enzymes?

    • #112121
      jonmoulton
      Participant

      "Also, in terms of the rate at which an enzyme acts, other than substrate concentration and reaction rate, are there any other conditions that would regulate the rate at which an enzyme works? Are there such thing as inherently "slower" or "faster" enzymes?"

      Oh my goodness yes yes yes. Different protein structures have different rates of catalysis – a single amino acid change can alter or eliminate activity. Temperature and pH affect rate. Many enzymes are controllable by other enzymes — look at allosteric regulation:
      http://en.wikipedia.org/wiki/Allosteric

    • #112126
      JackBean
      Participant

      Assuming you mean regulation of rate of one enzyme, then you’re interested in things such as posttranslational regulation (phosphorylation). As jonmoulton mentioned, allosteric regulators are important.

    • #112153
      rk386
      Participant

      So there is a difference between the regulation of the rate of one enzyme as compared to the regulation of the rate of many enzymes? How does the regulation of many enzymes work?

    • #112154
      JackBean
      Participant

      What I meant is the regulation of enzyme produced by one gene. On the other hand, as jonmoulton wrote, you can have several genes and the respective proteins will have different amino acids in active side, they may be localized in different compartments etc. But I do not consider this much as regulation, because you must have the gene already, so it’s not really something you can regulate, right?

    • #112157
      rk386
      Participant

      Do you mean that the same enzyme can be coded for by different genes?

    • #112161
      JackBean
      Participant

      That’s exactly what I mean. Actually most of enzymes is in form of isoenzymes coded by several genes.

    • #112164
      rk386
      Participant

      Thanks for explaining.

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