Write the balanced reaction catalyzed by phophoenolpyruvate carboxylase (P PC). Remember to add any cofactors, and to draw the structure formulas (a line-bond representation is fine) for the main substrate and product of the reaction.

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Chapter1: Biochemistry: An Evolving Science
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Write the balanced reaction catalyzed by phophoenolpyruvate carboxylase (P PC). Remember to add any cofactors, and to draw the structure formulas (a line-bond representation is fine) for the main substrate and product of the reaction.

Objective: The enzyme pyruvate carboxylase is discovered in a bacterium that was
thought not to contain it; in this case study, you'll see how researchers study and
characterize the enzyme, and, ultimately, show how it fits into a metabolic pathway.
Introduction: As one of the reactants in the first reaction of the citric acid cycle,
oxaloacetate is an important cellular metabolite. The concentrations of oxaloacetate are
tightly regulated.
Different organisms employ different mechanisms to obtain oxaloacetate. In
mammals and yeast, oxaloacetate is the product of the pyruvate carboxylase (PYC)
reaction. In E. coli, the enzyme phophoenolpyruvate carboxylase (PPC) provides
oxaloacetate from phosphoenolpyruvate (PEP) obtained from glucose oxidation in the
glycolytic pathway. If glucose is absent and E. coli is using acetate as a carbon source,
the glyoxylate pathway serves to generate the needed oxaloacetate. Usually, an organism
will employ PPC or PYC, but not both.
Detectable levels of PYC in the methanogenic bacterium Methanobacterium
thermautotrophicum had previously not been found, and since PPC had been detected, it
was believed that M. thermautotrophicum did not possess PYC. However, in the case
described here, microbiologists found that if they added biotin to cultures of the
methanogenic bacterium, pyruvate carboxylase activity could be detected. This was a
surprising finding, especially since it is known that the methanogen can synthesize its
own biotin. However, having identified the presence of the PYC enzyme, the
investigators set out to isolate, purify and characterize the enzyme. Purification of the
PYC was rather straightforward since the enzyme is soluble and hydrophilic. In addition,
the investigators were able to make use of the protein avidin, which binds to biotin with
high affinity and specificity.
Transcribed Image Text:Objective: The enzyme pyruvate carboxylase is discovered in a bacterium that was thought not to contain it; in this case study, you'll see how researchers study and characterize the enzyme, and, ultimately, show how it fits into a metabolic pathway. Introduction: As one of the reactants in the first reaction of the citric acid cycle, oxaloacetate is an important cellular metabolite. The concentrations of oxaloacetate are tightly regulated. Different organisms employ different mechanisms to obtain oxaloacetate. In mammals and yeast, oxaloacetate is the product of the pyruvate carboxylase (PYC) reaction. In E. coli, the enzyme phophoenolpyruvate carboxylase (PPC) provides oxaloacetate from phosphoenolpyruvate (PEP) obtained from glucose oxidation in the glycolytic pathway. If glucose is absent and E. coli is using acetate as a carbon source, the glyoxylate pathway serves to generate the needed oxaloacetate. Usually, an organism will employ PPC or PYC, but not both. Detectable levels of PYC in the methanogenic bacterium Methanobacterium thermautotrophicum had previously not been found, and since PPC had been detected, it was believed that M. thermautotrophicum did not possess PYC. However, in the case described here, microbiologists found that if they added biotin to cultures of the methanogenic bacterium, pyruvate carboxylase activity could be detected. This was a surprising finding, especially since it is known that the methanogen can synthesize its own biotin. However, having identified the presence of the PYC enzyme, the investigators set out to isolate, purify and characterize the enzyme. Purification of the PYC was rather straightforward since the enzyme is soluble and hydrophilic. In addition, the investigators were able to make use of the protein avidin, which binds to biotin with high affinity and specificity.
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