Citric Acid Cycle and Role of its Intermediates in Metabolism

Cell Biochem Biophys (2014) 68:475478

DOI 10.1007/s12013-013-9750-1

REVIEW PAPER

Citric Acid Cycle and Role of its Intermediates in Metabolism

Muhammad Akram

Published online: 26 September 2013 Springer Science+Business Media New York 2013

Abstract The citric acid cycle is the nal common oxidative pathway for carbohydrates, fats and amino acids. It is the most important metabolic pathway for the energy supply to the body. TCA is the most important central pathway connecting almost all the individual metabolic pathways. In this review article, introduction, regulation and energetics of TCA cycle have been discussed. The present study was carried out to review literature on TCA cycle.

Keywords TCA cycle Energetics of TCA cycle

Regulation of TCA cycle Amphibolic role of TCA

cycle

Introduction

The citric acid cycle was proposed by Hans Adolf Krebs in 1937. The citric acid cycle is the primary metabolic pathway for all the aerobic processes in an animal tissue. It is a series of reactions that are important for the cells: C2 units or acetyl-CoA that is derived from fats, carbohydrates and lipids [12]. TCA cycle utilizes (indirectly) about 2/3 of the total oxygen consumed by the body and generates about 2/3 of the total energy. The citric acid cycle is the nal common pathway for the oxidation of carbohydrate, protein and lipids. TCA plays an important role in gluconeogenesis, transamination, deamination and lipogenesis. Oxidation of acetyl-CoA by TCA cycle accounts for 2/3rd of total oxygen

consumption and ATP production. Acetyl-CoA is obtained from amino acids like leucine, tyrosine, isoleucine, lysine, phenylalanine and tryptophan, triacylglycerol, carbohydrates and ketone bodies. In aerobic organisms the TCA is amphibolic pathway, one that participates both in the catabolic and anabolic processes [3]. Through its role in the oxidative catabolism of carbohydrates, fatty acids and amino acids, the cycle provides precursors for many bio-synthetic pathways. Unlike the other metabolic pathways/ cycle, very few genetic abnormalities of TCA cycle are known. This may be due to the vital importance of this metabolic cycle for the survival of life. It has been observed that stimulation of Krebs cycle activity in the presence of ACTH may lead to increased production of steroid precursor(s) of corticosterone which in turn creates an increased demand for reducing equivalents for their conversion into corticosterone.

History

Albert...