Question

1) In one brief bullet point or sentence, state or explain the logic of why the individual polypeptides involved in purine biosynthesis must come together to form a multi-subunit enzyme.

2) Based on what you know about carboxylase enzymes that we have learned about in this course, what coenzyme would you predict would be part of 5′-Aminoimidazole ribonucleotide carboxylase. Justify your answer by citing an example in this course where that coenzyme was required in a carboxylase enzyme. Finally, state whether this coenzyme is utilized by 5′-Aminoimidazole ribonucleotide carboxylase by writing the sentence in this course that states the case. Cite specifically where this sentence was found. Please be brief – 3 bullet points are fine and one specific sentence.

3) In no more than 4 bullet points or 4 brief sentences, explain how the enzyme Glutamine-PRPP amidotransferase is regulated (activated/inhibited) by 5′-Phosphoribosyl-α-ᴅ-1-Pyrophosphate and adenosine diphosphate; and for each explain the logic of such a regulation.

Answer 1

1. Each polypeptide chain in such a protein is called a subunit. Protein synthesis occurs in cellular structures called ribosomes found outside the nucleus. The process by which genetic information is transferred from nucleus to the ribosome.

2. Carboxylase enzyme plays an essential role in regulating fatty acid synthesis and degradation. Recall that this enzyme catalyzes the committed step in fatty acid synthesis. It allow the production of carbon-carbon bonds by introducing HCO3- or CO2 into target molecule.

3. Glutamine PRPP amidotransferase catalyzes the first committed reaction of de novo purine pathway and is the key regulatry enzyme in the pathway.