[Studentofstuff123]

I read the forum rules, and hope you guys could help me.  The teacher gave us a take home quiz and said using the internet and working with friends is just fine because these catalytic reactions are extremely difficult to figure out.  We formed groups but everyone seemed pretty clueless as the examples in the book and notes are EXTREMELY different.  Most of the examples in the book are hydrolases and they are pretty obvious.  I was hoping for some help.

As a group we felt that

76) Isomerase, because the structure is broken down and by definition an Isomerase rearranges structural isomerism.

77) Ligase (Because on large protein is broken down into two)

78) Transferase as the OH is transfered to an OPO3

79) Unsure of this one, I know lyase adds a double bond but this one removed a double bond.  Not sure

80) Ligase

[AWK]

76 These are one letter codes for aminoacids
80 four-lettter code is used fo nucleic acid bases in DNA
77, 78, 79 - these reactions contain every biochemistry textbook (sugars and amino acids)

[Dan]

76. Isomerase is not an option. It is a multiple choice question. This is not an isomerisation - a peptide chain is being broken down.
77. Where do you see a protein? What do ligases do? Is that what is happening here?
78. Agreed
79. An amide is being converted to an amine. What class of chemical reaction is that? Hint: Acid to alcohol
80. Agreed

Look up the definition of each enzyme class in answers A-E (wikipedia will probably be sufficient), and find out which type of reaction they catalyse.

Match these reaction types to the reactions given.

[Studentofstuff123]

Ok

76) Lyase

77) Lyase again

79) Oxidoreductase (this ones the hardest for me)

[Dan]

Ok, I think you have 77 and 79 right now.

For 76: How are peptide bonds broken? What class of chemical reaction is it?

[Studentofstuff123]

Ok, I think you have 77 and 79 right now.

For 76: How are peptide bonds broken? What class of chemical reaction is it?

He gave a problem similar to that one on the board and said its a subclass peptidase.  However, above the hero there is a water molecule on the example and its a hydrolase.  In this case the water molecule is absent.

The only thing I can think of now as I look up definitions is that it's a transferase since one of the molecules is being donated to another.

[AWK]

http://en.wikipedia.org/wiki/Protease

[Dan]

He gave a problem similar to that one on the board and said its a subclass peptidase.  However, above the hero there is a water molecule on the example and its a hydrolase.  In this case the water molecule is absent.

It is a hydrolysis reaction. The amine terminus is on the left, acid terminus on the right (implicit from the nomenclature).

NH₂-(heptapeptide)-OH  NH₂-(dipeptide)-OH + NH₂-(pentapeptide)-OH

I agree though that this equation is not balanced - the should be water on the left side of the equation.

[AWK]

This is not a test. Just look which enzyme cuts peptide chain after Phe (F) or before Arg (R) and to which class it belongs.

[Babcock_Hall]

If you assign oxidation numbers to carbon atoms of the reactant and product and there is a net change in the oxidation numbers, then the reaction is an oxidation or a reduction.