Which enzyme of the citric acid cycle most closely resembles the pyruvate dehydrogenase complex in terms of its structure, organization, and the reaction it performs?

Question

BlackTom AI · Accepted Answer

When evaluating which citric acid cycle enzyme most closely mirrors the pyruvate dehydrogenase complex in structure, organization, and reaction type, several possibilities can be ruled in or out by comparing known features.

Option 1: isocitrate dehydrogenase. This enzyme functions as a single catalytic unit rather than as part of a multi-enzyme complex. Its role is to oxidize isocitrate to alpha-ketoglutarate with NAD+ (or NADP+) reduction, but it does not share the multi-component architecture characteristic of PDH. Therefore, it does not resemble the PDH complex in structure or organization.

Option 2: α-ketoglutarate dehydrogenase. This enzyme is the second large dehydrogenase complex in the cycle and belongs to the same family as the PDH complex: the α-ketoacid dehydrogenase complexes. These complexes are built from multiple catalytic components (analogous to E1, E2, and E3 in PDH) and use lipoamide cofactors to transfer the acetyl group with the same overarching mechanism. The reaction type is oxidative decarboxylation of an alpha-ketoacid (in this case, alpha-ketoglutarate) linked to CoA, mirroring the PDH mechanism, which makes this option the closest in both structure and function.

Option 3: succinate dehydrogenase. This enzyme participates in the citric acid cycle and links to the electron transport chain, but it is a flavoprotein that serves as a part of complex II of the respiratory chain rather than a multi-enzyme dehydrogenase complex like PDH. Its organization and function are distinct from PDH, making it an unlikely structural/functional match.

Option 4: malate dehydrogenase. Malate dehydrogenase is a single-subunit enzyme that catalyzes the reversible conversion of malate to oxaloacetate using NAD+/NADH. It does not exist as a multi-component complex and does not share the same type of prosthetic group usage or cofactor-sharing pattern seen in PDH, so it does not resemble PDH in architecture.

Putting these contrasts together, the option that best matches the PDH complex in terms of being a multi-enzyme, cofactor-sharing dehydrogenase and performing a similar oxidative decarboxylation step on an alpha-ketoacid is the α-ketoglutarate dehydrogenase complex.

BIOL3611.13541.202610 InClassChapter17&regulation

Which enzyme of the citric acid cycle most closely resembles the pyruvate dehydrogenase complex in terms of its structure, organization, and the reaction it performs?

查看解析

登录即可查看完整答案

类似问题

Acetyl CoA is the main form in which nutrients enter the.........................................

In going from acetyl-CoA to succinate, two carbons have entered the cycle and two have been released as CO2. Why is the cycle not considered as complete at this point?

In going from acetyl-CoA to succinate, two carbons have entered the cycle and two have been released as CO2. Why is the cycle not considered as complete at this point?

Which one of the following best indicates why citrate needs to be isomerized?

Of the enzymes of the citric acid cycle, which is not a freely soluble enzyme?

Which of the following situations or phrases most accurately describes the citric acid cycle?

In the first step of the citric acid cycle, it is important that side reactions such as undesired hydrolysis to release _____ be minimized.

ATP is a substrate for citrate synthase.

更多留学生实用工具

考试浏览器助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单