Regular consumption of meals rich in carbo - hydrate or administration of insulin initiates an increase in the amount of glucokinas e, phosphofructokinase , and pyruvate kinase in liver (Figure 8.23). These changes reflect an increase in gene transcription, resulting in increased enzyme synthesis. High activity of these three enzymes favors the conversion of glucose to pyruvate, a characteristic of the well- fed state (see p. 321). Conversely, gene transcription and synthesis of glucokinase , phosphofructokinase, and pyruvate kinase are decreased when plasma glucagon is high and insulin is low, for example, as seen in fasting or diabetes.