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Proteolysis of protease

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Proteolysis of protease

Postby CATIII » Fri Feb 20, 2009 10:28 pm

Hello!

I am in the middle of writing a lab report for an experiment conducted in my IB Biology class in which we used the enzyme lipase from pancreatin to break down trigylcerides found in milk at different temperatures. Pancreatin also contains the enzymes protease and amylase. I read more about protease and found out that it conducts proteolysis, which is the break down of peptide bonds between amino acids.

However, I know that lipase is a globular protein and thus basically a chain of amino acids. Does that imply that protease breaks down lipase by breaking down the peptide bonds between its amino acids? Or do the other bonds (ionic, hydrogen, sulfur bridges, etc.) within the lipase molecule prevent this from happening? I would appreciate an explanation.

Thanks in advance!
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Postby MrMistery » Fri Feb 20, 2009 10:57 pm

well, first of all i think you should understand what these enzymes actually are. "Lipase" is a general term for any enzyme that breaks down lipids. Each lipase is more or less specific to a particular bond in a fat molecule, and there are thus a lot of very different lipases. Same goes for protease and amylase. You used pancreatic lipase, pancreatic amylase and pancreatic protease.

Now, to address your question: yes, proteases do break down other enzymes. As a matter of fact, proteases will even break down other proteases. but the thing is that the concentration of lipase required to break down fats is so small that the lipase does its job way before proteases will chew it up.
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Re: Proteolysis of protease

Postby CATIII » Fri Feb 20, 2009 11:07 pm

Ahh ok, I understand! Thanks for the enlightenment :)
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Re: Proteolysis of protease

Postby JorgeLobo » Sun Feb 22, 2009 1:22 pm

Not quite all the answer. Understand that proteases refers to a large group of enzymes - each of which has a specificity - based on amino acid sequence, charge, size, etc.
For example trypsin cleaves peptide chains at the carboxyl side of the amino acids lysine and arginine, except when either is followed by proline.
The "lipase" you describe may or may not fit in to the specifity for the "protease" in question.
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Re: Proteolysis of protease

Postby CATIII » Tue Feb 24, 2009 7:27 pm

That does make sense. Would you happen to know whether pancreatic lipase fits into the specificity of pancreatic protease?

I have another question though. Our teacher told us that triglycerides (found in ordinary milk) are hydrolyzed into monoacylglycerid [or monoacylglycerol maybe?] + 2 fatty acids by pancreatin; however, in a biochemistry book and on the internet it says that triglycerides are hydrolyzed into glycerol and 3 fatty acids. I was wondering if anyone happens to know the products of the hydrolysis by pancreatin (pancreatic lipase): monoacylglycerol + 2fa or glycerol + 3fa?
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Postby MrMistery » Sun Mar 01, 2009 2:51 pm

first the acyl bond with one fatty acid is hydrolyzed, yeilding diacylglycerol. then a second bond is hydrolyzed, yielding monoacylglycerol. then the third one, and you are left with glycerol and 3 free fatty acid molecules
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