For example food digestion enzymes, protein building enzymes, enzymes working in immunity?...and do we know if they have to "be" in a certain tertiary or Quaternary structure to function properly? Any knowledge or "I would think..." on this?
Would we know if they loose their ability to work properly if they change structure? Any good articles on this?
Cold but cosy up here in the North ;c))
anna
Hi,
This is not a "we think" but "we know". There are numerous examples in the literature of inactivated enzymes. Inactivation by mutations, by binding of an inhibitor, by changing the temperature or the pH (leading to structural changes that can be extremely subtle - you can look for the corresponding articles in the literature, they are easy to find). But you may also think about cooking, i.e. heat denaturation as when cooking egg whites. W.R.T. temperature for example, the enzymes of a given organism have adapted such as to have the required flexibility necessary for catalysis at the physiological temperature of the organism.
Hence psychrophilic enzymes will be "soft", and too flexible at higher temperatures. They "will be cooked" at lower temperatures that those of mesophilic enzymes. Hyperthermophilic enzymes won't have enough flexibility until the "appropriate" temperature. Discussed in the literature again...
Hello Anna,
Any text book on Biochemistry talks about it in very detail.
Andrei
There is a data base for enzymes http://enzyme.expasy.org/ where you can find many useful links and information
Maria
I second the suggestion made by Tomáš Hluska to look at the Protein Data Bank (PDB), it is a fantastic resource for those that are interested in looking at protein structure since it allows you to download protein structures which can be opened by any good protein modeling software (Pymol, SwisPDB to name a few) for further manipulation.
In regards to your question about structure vs function. It has long been understood that the structure is inherently linked to function. This can be due to the fact that the fold brings the critical amino acids involved in catalysis into the correct orientation with the substrates or for other reasons such as the beta barrel structure within GFP limits the quenching of fluorescence via the expulsion of water molecules. However don't become misled. It is true that complete unfolding of the protein will result in loss of function however it has been seen that small structural changes to the backbone will firstly not always lead to loss of function but secondly, in some cases can even enhance function. Good articles to read concerning this would be the following:
http://www.cell.com/structure/pdf/S0969-2126(14)00115-4.pdf
http://www.ncbi.nlm.nih.gov/pubmed/17662719
Hope this helps :)
For enzymes, structure = function, but function is not limited to catalytic activity. Enzymes can also have structural features involved in regulating their activity. For example, proteases involved in digestion such as trypsin and chymotrypsin are synthesized in an inactive form (trypsinogen, chymotrypsinogen) that is activated by proteolytic cleavage. Some enzymes have binding sites for regulatory (allosteric) ligands that increase or decrease their activity. Additionally, the structure of an enzyme can include post-translational modifications, such as phosphorylation (example: glycogen synthase) that affect activity.
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