内分泌 信号传导 10.pdf

Environmental Signaling (ES-101) Case 10: Messing with Synthesis Session Objectives Students will be able to: Describe the synthetic pathways for steroid hormones, and how some enzymes make bottlenecks in this pathway Explain the special position estrogen seems to hold in that pathway Describe the unusual nature of the genetics of the P450 enzymes Identify compounds which might create endocrine disruption by messing with synthesis of steroid hormones In this class students examine the biosynthetic pathway for steroid hormones and test their hypotheses about the effects of disabling specific enzymes. Show the students the main page of the supplementary webpages, and look at the overall pattern of the pathways. Sequentially ask them the questions below and then test their hypothesis by clicking on the specified enzyme to see its effect. Looking at the displayed diagram of steroid hormone biosynthesis, make a prediction. Do you think each step is controlled by a unique enzyme? Click on the arrow between pregnenolone and 17-HO pregnenolone. Discuss with them what you see. Where in the diagram are the corticosteroids? Is there one enzyme that forms a bottleneck in their synthesis? Click now on the arrow between progesterone and 11-deoxycorticosterone. Discuss with them what you see. What is special about the positions of Testosterone and Estradiol in the pathways? Click now on the arrow between androstenedione and testosterone, 5-alpha reductase, and testosterone and estradiol. Talk about these special patterns. Which enzymes control multiple pathways? Divide the class into 4 groups, giving each two model sets and assigning them one of the chemical pairs below. This simulation has given some hints about the functions of the enzymes in these pathways. Now you are going to work in groups to build the chemicals on either side of an enzyme, comparing them to see what work the enzyme has done. It will probably be easiest to