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Effect of pH on amylase activity

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Effect of pH on amylase activity

Postby cracked_doc » Fri Oct 13, 2006 7:14 pm

What happens to the activity of amylase when put in a solution containig starch at pH 11? what is the simplest test to tell that starch has been converted into maltose?(i know abt the Benedicts test).
thanks in advance
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Postby BioCell » Fri Oct 13, 2006 11:14 pm

So, thing is... there is an optimum pH for every enzyme. pH is capable of altering the structure of the active center in the enzyme causing denaturation.

The optimum pH is not a solid value. Usually they work quite well within a ph range (note that there are those that will work properly in any pH value) Out of this range they will act slowly tending to no inactivity (cause of denaturation).

From NO confirmed sources I got this values:

Salivary amylase or Ptyalin > 5.6 - 6.9 (http://en.wikipedia.org/wiki/Amylase)
Pancreatic amylase > 8 - 9 (http://www.fed.cuhk.edu.hk/~johnson/php ... php?p=218&)

It seems that at a pH of 11, amylase will not act at its optimum performance.

As for the test I recommend you to visit http://samson.kean.edu/~breid/enzyme/enzyme.html

I think we used to use bread as a starch source.
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Postby lara » Sat Oct 14, 2006 9:41 am

test-y not iodine to test the presence of starch?
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Postby cracked_doc » Sat Oct 14, 2006 9:42 am

thanks alot for the help...i wanted to ask that can this be a test : as starch is insoluble in water so the solution we make with water will be kind of a suspension but when by the action of amylase it will convert into maltose (which is soluble in water), the starch would be converted into maltose and make a solution which would indicate the presence of maltose....kinda stupid i guess.
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Postby cracked_doc » Sat Oct 14, 2006 9:44 am

_at_ lara :I need a test for the presence of maltose in the solution ...
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Postby victor » Sun Oct 15, 2006 3:19 am

cracked_doc wrote:thanks alot for the help...i wanted to ask that can this be a test : as starch is insoluble in water so the solution we make with water will be kind of a suspension but when by the action of amylase it will convert into maltose (which is soluble in water), the starch would be converted into maltose and make a solution which would indicate the presence of maltose....kinda stupid i guess.


Well, there're two amylases here. One is alpha-amylase which convert starch into maltose and dextrines (note, there are amilodextrin, erithrodextrin, and achroodextrine); while the other, beta-amylase, will convert starch into maltose only. Ooh...starch in water is not forming a suspension, but colloid.

And for a test for maltose presence in solution, first, you can use iodine 0.01 M solution (if you obtain the maltose from starch) to detect the presence of long chained glucose polymer like dextrines. Test it by dropping 1 drop of iodine solution into 1 drop of your sample, the color indication would be:
blue = starch
purple = amylodextrine
red = erithrodextrine
colorless = achroodextrine, maltose, or glucose

Since the colorless result indicates the presence of maltose and dextrine, you can wait for a little bit time to make sure that the dextrine is fully degraded into maltose by the enzyme. After that, you can test the presence of maltose by doing Benedict's test. Green to vermilion color followed by sedimentation of Cu2O is an indication of maltose presencee since it's a reducing sugar. Well, at least that's for the qualitative test...:mrgreen:
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Postby victor » Mon Oct 16, 2006 11:30 am

Ummm....a little bit correction about amylase...:mrgreen:
Well, as we know, there are three amylase enzymes which are alpha amylase, beta-amylase, and glucose-amylase.

Alpha-amylase = an enzyme which cuts down starch randomly in position, but it can't cut the branch (alpha-1,6) position. So, if a starch solution is given this enzyme, it will yield glucose, maltose, and various dextrins.

Beta-amylase = an enzyme which cuts down starch from one tips to another by each two molecule, but still, it can't cut the branch position (alpha-1,6). So, if a starch solution is given this enzyme, it will yield maltose, and various dextrins.

Glucose-amylase = same like beta-amylase but it cut per one molecule. So, if a starch solution is given this enzyme, it will yield glucose, and various dextrins.

Our body made an enzyme called "debranching enzyme" to cut starch in branch position (alpha-1,6).

Note: glucose-amylase only occurs in bacteria
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Postby cracked_doc » Tue Oct 17, 2006 4:18 pm

thanks ..that was really comprehensive...i've grasped the concept..:)
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