Suppose you are working in a research lab investigating the expression of the enzyme hexokinase in Drosophila. Specifically, you are interested in expression patterns of this enzyme in Drosophila in the larval stage vs. the adult fly stage. After collecting data from both larvae and adult flies, your analyses indicate that the rate of transcription of the hexokinase gene is similar during both life cycle stages. However, measurements of the enzyme activity during each of the two stages show dramatically decreased levels of hexokinase activity in the adult flies compared to the larvae. Explain why this might be the case.