Question

Only the liver form of pyruvate kinase is inhibited by alanine.

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1. The liver is the_____active gluconeogenic tissue. Since alanine is an important gluconeogenic _____ its accumulation in liver is a signal that gluconeogenesis should be_____
2. In addition, alanine _____in muscle under conditions of high metabolic demand, where glycolysis must still function to provide _____

O product
O inhibited
O ATP
O precursor
O least
O ADP
O accumulates
O is quickly consumed
O activated
O catalyst
O most
O NAD

Answer 1

Pyruvate kinase is a liver enzyme regulated by alanine, phosphorylation, and ATP, which indicates the cell's energy status and modulates the glycolysis pathway.

Step-by-step explanation:

The enzyme pyruvate kinase plays a pivotal role in glycolysis, the process by which glucose is converted into pyruvate, yielding energy in the form of ATP. In the liver, pyruvate kinase is subject to complex regulation, including inhibition by the amino acid alanine. This is a feedback mechanism; when alanine levels are high, it indicates that sufficient energy is available, and hence, the conversion of pyruvate to ATP is downregulated. Additionally, the enzyme is allosterically activated by fructose-1,6-bisphosphate, an intermediate in glycolysis, aligning the enzyme's activity with the cell's energy demands.

Regulation also occurs through phosphorylation and dephosphorylation, with phosphorylation reducing activity, and dephosphorylation increasing it. Moreover, ATP serves as a negative allosteric regulator of pyruvate kinase, signaling that the cell has ample energy, and downshifting the glycolytic pathway. Disruptions in the normal functioning of pyruvate kinase can have serious implications, as seen in various mutations that affect enzyme production, activity, and stability, which highlights the critical nature of this enzyme in cellular metabolism.