[mythonline]

Hello,

I am a med student in the 2nd semester, and I am having a bit troubles with understanding the types of reactions some co-factors are involved in, and I am not sure that those I do know, don't have another way of reacting.

NAD+
Dehydrogenation of a non-carbon atom that is connected to the chain from one side, and have hydrogen on it to form double bond between him and the carbon (for example hydroxy group would go into oxo group).

NADPH
opposite of NAD reactions?
hydroxylation? (difference between NADPH to other hydroxylation cofactors?)

FAD
Dehydrogenation of 2 carbons inside a chain to form double bond between them

Dihydrobiopterin (BH2)
my book giving him almost the same explanation as NADP, could someone tell me the difference?

molybdopterin
written to create electron transfer reaction, could someone give more knowledge about this enzyme?

ubiquinone
accept slowly electrons and protons? what does it mean?

Lipoate
can someone explain?

haeme-Fe3+ non-haeme-S-Fe+
transfer of one electron? (I remember something vaguely about CO2 to carbonic acid, but could someone give further information?)

glutathione
donor of 2H (different between the rest of the 2 hydrogen donors?)

pyridoxal phosphate
just transamination?

PAPS
transfer of sulfonic group?

carboxybiotin
transfer of carboxylic acid?

what is the difference between the reaction of transfer of acyl group between acyl-CoA and dihydrolipoate? same question about SAM and cobalamin? which types of substances the body will use for those reactions?

thiamin diphosphate, transfer of oxo group? what does it mean?

thanks for any *delete me*

[Babcock_Hall]

What does your textbook say about each of these cofactors?  I suggest picking up a copy of Geoffrey Zubay's Biochemistry, 4th edition, and look in Chapter 11.  That is quite a list you have, but I might be able to help you avoid some pitfalls.  With respect to NAD/NADH and NADP/NADPH, both are involved in hydride transfer reactions, but NADPH is more commonly seen in biosynthetic reactions.  In hydroxylation reactions, NADH supplies electrons (sometimes through another cofactor), but O2 is typically the source of the oxygen for the hydroxyl group.  NADH dehydrogenase (Complex I) is found in the mitochondria.  What does that suggest about the role of NAD? 

Iron-sulfur clusters are mostly involved in 1 electron transfers, but aconitase in the Krebs' cycle is an exception.  Ubiquinone is found in the membranes.  Look into the electron transport chain of mitochondria.  Pyridoxal phosphate is used for many reactions of amino acids besides aminotransferases.  Think about the conversion of histidine to histamine, for example.  TPP is used for the making or braking of carbon-carbon bonds in which one of the carbons is part of a carbonyl group.  The pyruvate dehydrogenase complex uses it.  Lipoate is also cofactor in the pyruvate dehydrogenase complex.