Step 6 - Succinate Dehydrogenase
반응
Succinate + FAD → Fumarate + FADH₂
Succinate + FAD ──(Succinate dehydrogenase)──→ Fumarate + FADH₂
핵심 정보
| 항목 | 내용 |
|---|---|
| Reactant | Succinate (C4), FAD |
| Product | Fumarate (C4), FADH₂ |
| Enzyme | Succinate dehydrogenase |
| 산물 에너지 | FADH₂ (~1.5 ATP) |
중요성: TCA Cycle과 ETC의 연결 효소
Succinate dehydrogenase는 이중 역할:
- TCA cycle의 Step 6 효소
- ETC의 Complex II (Succinate dehydrogenase) = 미토콘드리아 inner membrane에 내장
“There is an unusual additional respiratory chain complex that is an important component of the citric acid cycle, where it is known as succinate dehydrogenase. This membrane-embedded enzyme captures electrons during the conversion of succinate to fumarate and passes these electrons directly into the electron-transport chain via a flavin electron carrier (FAD).” — Chapter 14
Figure 14-26: Succinate dehydrogenase 구조. FAD 포함 4개의 서브유닛.
특징
- FAD를 electron acceptor로 사용 (산화 정도가 작아 NAD⁺보다 낮은 redox potential)
- 전자를 ubiquinone으로 직접 전달 → Complex III로 이동
- Proton pump 아님: Complex II는 proton을 pumping하지 않음
→ Complex II (Succinate dehydrogenase)