Re: What is the difference between bacterial amylase and salivary amylase?

Hi Lloyd,

Here is some background information that you might already know: Salivary 
amylase is a digestive enzyme found primarily in your saliva.  It breaks 
down carbohydrates (sugars) in the food you eat.  Salivary amylase also 
acts as a substrate for bacterial colonization on your teeth, by binding to 
your enamel and providing a linking site for bacteria that can bind to 
amylase.  So there is a trade off, in that salivary amylase promotes 
bacterial colonization (and therefore plaque formation and tooth decay) but 
also helps to digest your food before it even gets to your stomach.

Bacterial amylases appear to vary more than salivary amylases, probably due 
to the fact that microbes occupy many different types of environments 
whereas one person's mouth isn't much different from another person's 
mouth.  In one review article from the journal titled Advances in Applied 
Microbiology, the authors list a number of bacterial amylases that they 
studied.  Each of these was thermophilic, and some were also alkalophilic 
bacteria.  This means that the amylases are heat-stable. The heat-stability 
makes bacterial amylase suitable for commercial processes, such as the 
production of dextrose from the breakdown of starch by amylases.  When the 
authors studied the pH of the environments in which they found the 
different species of bacteria, the optimum pHs ranged from pH 4.0 to 11.0.  
You might want to look up some information about the amylase from the 
particular bacterium that you studied.  You will probably find that the 
organism lives in a slightly acidic environment.

In general, enzymes differ from organism to organism by amino acid residues 
of the primary structure of the enzyme.  This harkens back to genetics, 
since the genetic make up of an organism dictates the structure of the 
enzyme.  If you do a search of the DNA sequence of the two amylase genes, 
you will probably find that they differ slightly.  As a result of these 
genetic differences, the structure of the two enzymes will differ slightly 
as well.  

I hope that this helps!  Good luck with the experiments.

Sarah Earley
CU Boulder