Regulation of Metabolic Pathways

Anabolic pathways are frequently stimulated under conditions of abundance (ie, high levels of cellular energy and availability of precursor molecules for the pathway) and inhibited when energy and precursors are low. 

Catabolic pathways are often activated by conditions involving low energy and are inhibited when energy and building blocks are available at high levels. 

The rate or flux of substrates through a pathway is also dependent on substrate availability. 

One of the major mechanisms for regulation of preexisting enzymes is via covalent modification, usually by protein phosphorylation or dephosphorylation. 

This is an important mechanism because it is rapid, reversible, and economical for the cell and body. 

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E. Hormonal control provides a major means for regulation of metabolic pathways,... 

For the regulation of metabolic pathways metabolites are often used which are a product of that pathway. The basic strategy for the regulation is exemplified in the mechanisms employed in the biosynthetic and degradation pathways of amino acids, purines, pyrimidines, as well as in glycolysis. In most cases a metabolite (or similar molecule) of the pathway is utilized as the effector for the activation or inhibition of enzymes in that pathway. 

Regulation of metabolic pathways. The regulatory mechanisms for the rate-limiting enzyme of a pathway always reflects the function of the pathway in a particular tissue In feedback regulation, the end product of a pathway directly or indirectly controls its own rate of synthesis in feedforword regulation, the... 

You may have noticed by now that regulation of metabolic pathways in the human is exceedingly complex this might be called the second principle of metabolic regulation. As you study different pathways in the subsequent chapters of the text, it may help to develop diagrams such as Fig. 9.15 to keep track of the function and rationale behind different regulatory interactions. 

Regulation of metabolic pathways occurs at rate-limiting steps, the slowest steps, in the pathway. These are reactions in which a small change of rate will affect the flux through the whole pathway. 

Nucleotides play a central role in the regulation of metabolic pathways and their quantification in biological samples is of fundamental importance. There is an enormous variety of nucleotides (i.e. the four... 

To study the role of the mitochondrial transport systems in the regulation of metabolic pathways as they occur in the intact cell, knowledge of the mitochondrial... 

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