You are studying the effects of the addition of a novel compound to the chow of laboratory animals on the overall rate of flux through glycolysis. You discover that when the animals consume the mcompound containing chow, there is an increase in glycolytic flux to pyruvate. Examination of serum hormone levels in these animals indicates a change in the ratios of several key regulators of glucose homeostasis. The consumption of the test compound most likely causes an increase in which of the following hormone ratios, thus best explaining the observed changes in the rate of glycolysis?

Question

Quizplus · Accepted Answer

An increase in the insulin to glucagon ratio promotes glycolysis by enhancing glucose uptake and utilization, which aligns with the observed increase in glycolytic flux.  As the level of insulin rises, there will be a concomitant increase in the activity of phosphodiesterase within responsive cells, such as the liver. The phosphodiesterase will hydrolyze cAMP leading to reduced activity of PKA. As the activity of PKA falls, the level of phosphorylation of 6-phosphofructo-2-kinase, PFK2 will fall which reduces its phosphatase activity. When functioning as a phosphatase, PFK2 hydrolyzes fructose-2,6-bisphosphate (F2,6BP) to fructose 6-phosphate. When PFK2 is not phosphorylated, it acts as a kinase and will, therefore lead to increased levels of F2,6BP. Conversely, as the level of glucagon increases, the activity of PKA increases leading to increased phosphorylation of PFK2. This in turn results in decreased F2,6BP levels due to the phosphatase activity of PFK2.

You Are Studying the Effects of the Addition of a Novel