Enzymes #2

Achim Recktenwald, PhD achim at ibex.ca
Tue Dec 3 08:15:24 EST 1996

Melissa M wrote:
> Hello,
> I am still a little unclear about a few things. Okay is this right? An
> enzyme cannot function unless here is a co-factor along with it (why is
> that) 

This is not true. there are many enzymes that do not need any cofactors;
e.g., many hydrolases, like proteases.

There are two different
> co-factors metal ions and co-enzyme. 

Metal ions allow chemical 'routes' not possible with the standard
elements available in amino acids. If you want to get an idea what kind
of reactions enzymes with metal ions can perform, check out the
following book(let):
David E. Fenton: Biocoordination Chemistry, Oxford Science Publications,
I got it a few weeks ago in a local university bookshop for ~CDN$ 10.

There is something that causes a
> reduction to occur. What is that process called?? 

Are you talking about redox reactions? E.g., all reactions involving
NAD(P)H are redox reactions. The enzyme uses NAD(P)H to reduce a
molecule, at the same time NAD(P)H is oxidized to NAD(P)+. In the
reverse reaction the enzyme oxidizes a molecule and NAD(P)+ is reduced
to NAD(P)H. 

And also how does ATP
> and NAD and NADH evolve? I do not understand this. It seems from my
> reading that they suddenly evolve, no chemical reactions what so ever?

I am not quite sure what you mean by 'evolve'. Are you talking about the
evolutionary appearance of the molecule or are you asking where these
molecules are produced in the cell, so that the enzymes can use them for
their reactions. Concerning the first point, I have no idea myself,
concerning the second point, they are synthesized by the cells (see any
biochemistry textbook) and used by cells in many different reactions.
The ATP and NAD(P)H molecules are constantly regenerated (from AMP or
ADP, and NAD(P)+) during the energy production processes from 'food';
e.g., in aerobic cells by glycolysis, TCA-cycle, and subsequent
oxidative phosphorilation of sugars.

Hope this helps.


> If you could help me it would be ever so appreciated for I have a test on
> this on Tuesday!!!
> Melissa

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