Question

Question 7 3 pts A second biochemist also studying metabolism feeds her rats 3-[14C]-alanine (alanine labeled at the methyl group). Alanine can provide carbons for gluconeogenesis because of the reaction catalyzed by alanine aminotransferase. alanine + a-ketoglutarate = pyruvate + glutamate After sacrificing her rats she finds considerable 14C in the glucose. Where is the 14C located in the glucose? C1 C2 C3 C4 C5 C6

Answer 1

If Methyl carbon of pyruvate is labelled and it enters gluconeogenesis pathway, then the C1 and C6 of glucose are labelled formed through various reversible steps just opposite to that of glycolytic pathway including formation of Pep from pyruvate, then 2- phosphoglycerate, then 3- PG, 1,3- bis PG, glyceraldehyde 3- phosphate, dohydroxyacetone, so on and finally converted into glucose.

In the given problem methyl carbon of alalnine is labelled which is converted to pyruvate in presence of alanine aminotransferase producing methyl carbon of the pyruvate labelled which then enters gluconeogenesis pathway and form glucose labelled at C1 and C6 as explained below:

Solution: alanine aminot Alamine + X-KG - Pyruvate + glutamate -ooc Coo- -o0c-cu-C4, --com- * CH₂ - C - Coo- Coo Ch2 - the C=0 (labelled (140 Hocantung coo- 2 Pyruvate Coo---- gluconeogenesis 1 Glucose CHO H-2C-OH (Carbon no.w.tt. 03eyruvate COO COO- .00 2 2 C=0 C=0 3l3 3 CH2 Ho-ċH 31 H--04 H2OH. * C1 and c6 of will be labelled. 3*) muelliyl.c. glucose So, the correct answer is c1 and C6.