MadSci Network: Biochemistry
Query:

Re: why do bacterial and fungal amylase have different optimum temperatures?

Date: Thu Jan 26 05:20:28 2006
Posted By: Neil Saunders, Research fellow
Area of science: Biochemistry
ID: 1138220034.Bc
Message:

Dear questionner,

Thanks for your interesting question. You don't mention which bacterium and which fungus you were studying, so my first question to you is: what temperature do those organisms normally grow at? Is one very different to the other? Do the optimum temperatures of the amylase make sense when you think about the growth temperature?

Let's think some more about proteins and enzymes. There are many enzymes, like amylase, that are found in all different kinds of organisms - bacteria, fungi, plants, mammals. You and I also have amylases - one that we secrete in saliva and another secreated by the pancreas. Now, these organisms live in many different types of environment. To take just the bacteria, they may live in boiling hot springs, freezing Antarctic lakes, salty soda lakes, acid drainage water from mines or more benign, comfortable places such as in our digestive tract.

Many of those bacteria probably contain amylases and there will be many other proteins that they have in common. However, in each case, the enzymes need to be optimised so as to function in their environment. If you looked at the protein sequences of those enzymes you would see that the key amino acids - those that are involved in the catalytic reaction - are probably the same. However, the rest of the protein will vary in enzymes from different sources and those variations are what lead to different properties (such as optimal temperature) in the enzymes. Yes, your enzymes are both amylases, but they're not the same amylase. You might find that amylase from the boiling water bacterium contains more non-covalent bonds to make it stable at high temperature, or that amylase from an Antarctic bacterium contains more of some types of amino acids that make it flexible and active at low temperature.

If you're interested in looking at this further, you could explore the Protein Data Bank website. You can type in a simple query such as "amylase" and the site will show you the structures of amylases from all kinds of organisms. You can browse through, look at the structures and sequences and see what makes the amylases the same, what makes them different.

Hope this answers your question,
Neil


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