|MadSci Network: Biochemistry|
Sounds like an interestting experiment, and as far as your hypothesis, you seem right on track. Although I have no expansive knowledge on the physiology of cod livers, I do know a little about catalase. Catalase is an enzyme that breaks down hydrogen peroxide, thus preventing the damage that can accrue in cells due to the oxidizing nature of this chemical. It is present in all cells, but at much higher concentrations in the liver because this is the main detoxifying organ of the body.
OK, so your question in should liver catalase work at a different temperature in a cod versus a lamb? You'll have to prove it yourself, but I would say that they do work best at different temperatures. They do the same thing, but why should they work more efficiently at different temperatures? Well, that could be explained by a difference in protein sequence that would affect temperature stability. I tried looking for catalase sequences in fish to compare with something along the bovine species, but unfortunately I wasn't able to find any. The point is though, that the sequence of DNA for each catalase gene is obviously similar enough to catalyze the same reaction, but may vairy slightly so that each gene is active at a particular body temperature. This difference may only be a few amino acids out of the thousands that compose this protein. How? The enzyme has to have a particular shape to perform its function. Temperature, whether it is too hot or cold, alters protein shape by changing the availability of the active site and altering the proximity of important amino acid reative groups. Compared to us say, a species that lives at hotter temeratures may have a different amino acid sequence so that its catalase enzyme remains stable at eleveated temperatures. Put our catalase enzyme at this same elevated temperature at it is less active or even denatured(a fancy science word for destroyed) depending on how much higher the temperature is. So it would make sense for catalase enzymes of a lamb and cod to work best at different temperatures. How much different you'll just have to do more experiments to find out.
I don't know of anyone doing experiments such as this unfortunately. Also I don't know how your are going about the experiment, specifically your catalase isolation and testing. I also don't know if you have anyone to help you. Here is a way to break open cells in tissue so that perhaps you can better purify catalase to test it's activity. Maybe you have access to these chemicals and equipment at school. "Organs, tissues, or tissue culture cells were homogenized in 7 mM pyrophosphate buffer (pH 8.3). The homogenates were centrifuged at 550 x g for 5 minutes. The supernatant solutions were used for the assay." This was taken from a paper on Methods for the Detection of D-Amino-Acid Oxidase, by Ryuichi Konno at the Department of Microbiology, Dokkyo University School of Medicine, Mibu, Tochigi 321-0293, Japan. (E-mail:firstname.lastname@example.org) It is the closest and easiest thing I could find on the web. You can search for biology protocols on line at Biological Procedures Online. The rest of the paper isn't necessary for you to read cause the assays are different as the enzyme is different. The point is that if your methods of isolation the protein are better, then so will your ability to perform the test with accuracy and repetition. If you need any advice feel free to send me an e-mail. Good luck,
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