PLEASE HELP- THIS IS TIME SENSISTIVE! PART ONE: Aminotransferases are enzymes th

Question

PLEASE HELP- THIS IS TIME SENSISTIVE!

PART ONE:

Aminotransferases are enzymes that catalyze the interconversion of amino acids and - keto acids. They serve the important metabolic role of allowing the carbons in amino acids to be used for carbohydrate synthesis.

Aspartate aminotransferase catalyzes this reaction: aspartate + a-ketoglutarate <--> oxaloacetate + glutamate

Alanine aminotransferase catalyzes this reaction: alanine + a-ketoglutarate <--> pyruvate + glutamate

Be sure to look up the structures of these compounds if you don't know them. Two biochemists are investigating the synthesis of glucose from dietary amino acids. Biochemist 1 obtains 4-[14C]aspartate (aspartate that has 14C at the sidechain carboxyl) and feeds it to rats. After sacrificing the rats, he is unable to detect any significant amounts of 14C in glucose. Biochemist 2 obtains 3-[14C]alanine (alanine that is labeled at the sidechain methyl group) and feeds it to rats. After sacrificing the rats, she finds that the glucose isolated from the rats does contain significant amounts of 14C-glucose.

Which enzyme catalyzes the reaction that is responsible for the loss of 14C that is observed by Biochemist 1? aspartate aminotransferase, PEPCK

pyruvate carboxylase, or enolase?

PART 2:

Consider the result obtained by Biochemist 2 in the experiment described above. Where is the 14C located in the glucose isolated by Biochemist 2?

C1, C2, C3, C4, C5, or C6?

PART 2:

Consider the result obtained by Biochemist 2 in the experiment described above. Where is the 14C located in the glucose isolated by Biochemist 2?

C1, C2, C3, C4, C5, or C6?

Explanation / Answer

1. PEPCK (Phospholenolpyruvate carboxykinase) is responsible for the loss of 14C that is observed by Biochemist 1, as this is the enzyme which performs decarboxylation in the process of gluconeogenesis.

2. It should be C6. It is easy to attach at C6 because of low hinderance and high reactivity.

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