Question

Question 7 3 pts A second biochemist also studying metabolism feeds her rats 3-11C)- 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 0 0 0 0

Answer 1

This is a simple question once you understand the exact reaction mechanism from the alanine until reaching the glucose molecule. This occurs through the glucose-alanine cycle. The aminotransferase reaction converts alanine into pyruvate, and such pyruvate then transforms into glucose (2 pyruvates needed).

The enzyme interchanges the amino group from the alanine and the keto group from the ketoglutarato:

Note the black circles, those are the labeled 14C.

t o Ntly Glutamate Pyruvate Alanine Ketoglutarate

Now the next reaction is two pyruvates forming the glucose molecule. There are a lot of intermediate redox reactions here, but the two pyruvates take the following places:

Note the two pyruvates are taking place to show what will be the configuration. The circled carbons are the 14C labeled. Now we can see them in the resulting glucose. The positions are C1 and C6

O OOOH OH OH OH Two pyruvates Glucose