The question is referring to the hexosamine pathway.
Carbamoyl phosphate and arginine are involved in the urea cycle. So is n-acetylglutamate (NAG) (regulates production of carbamoyl phosphate).
Hexoasmine pathway has been implicated in Insulin resistance and diabetic nephropathy! https://www.ncbi.nlm.nih.gov/pubmed/10997685 (Just was curious why NBME asked this!!!)
I tried to use logic to answer this question (I did not know about the hexosamine pathway). Here is my attempt--this is probably wrong somewhere.
I figured that if you want to make glucosamine, you need to combine glucose + an amine group
(A) Arginine I knew was involved in donating nitrogen, but it is in the urea cycle, so I figured this was probably not the answer but it had potential. I figured that the major way this compound removes its nitrogen is through urea, though.
(B) ATP. Since F6P already has the phosphate group, I figured ATP is probably not necessary as the compound in question already has a PO4 group.
(C) Carbamoyl phosphate. I knew this was involved in both the urea cycle and nucleoside synthesis, so this was less likely. It also is the product of a NH3 and CO2 so that means that I wouldn't expect it to donate an amine group
(D) Glutamine I figured has an amine group attached to it ready for donation. I also know that transamination reactions are common with amino acids and alpha-ketoacids (e.g. alpha ketoglutarate with alanine can get you glutamate and a pyruvate via ALT) thus it made sense that an amino acid could donate an amine group.
(E) The only thing I knew about NAG was that it was used in the urea cycle as an allosteric activator of CPS, so I didn't think that it was useful as a donator of nitrogen since its function is to help aid nitrogen excretion.
So then I was stuck between A and D, but based on transamination reactions, I picked D.
you need to add an amine (nitrogen) and most biochem processes from sugar --> amine requires glutamine
If you want to take a look for the clinical importance of the hexosamine pathway & products: https://www.sciencedirect.com/topics/neuroscience/hexosamines
Process of elimination on this one.
submitted by ∗seagull(1933)
out of curiosity, how may people knew this? (dont be shy to say you did or didnt?)
My poverty education didn't ingrain this in me.