BCH4024 F25 E2 Q6:  A 3 day-old male infant has poor feeding…

BCH4024 F25 E2 Q6:  A 3 day-old male infant has poor feeding, decreased muscle tone, and several seizures per day. Lab tests show elevated levels of lactate, massive elevations of fumarate, and decreased levels of malate. You suspect a problem with the citric acid cycle.  What enzyme deficiency would most directly lead to these lab test results?