Problem: Scientists are trying to engineer E. coli to produce fumarate. They already successfully constructed a succinate producer with a good titer and yield (Jantama et al., Biotechnol Bioeng. 2008 Apr 1;99(5):1140-53). They inactivated fumarate reductases encoded by frdABCD shown in the right figure with the hope to accumulate fumarate as a final product. However, when they did that, malate accumulated instead of fumarate. Can you explain why this plan failed? Need Assignment Help?