How does the cell regulate different metabolic pathways?

Question

I heard somewhere that cells use different nucleosides bound to triphosphates e.g. ATP, GTP, CTP and other modified compounds: NADH, NADPH to distinguish between different metabolic pathways and so they regulate where they use up the energy. I heard that kinases play an important role in the regulation. Is there a connection (I guess there is if I check NADPH)? Is this regulation mapped? I mean is there a simple map which contains the main processes and the energy carrier and regulatory compounds?

I am looking for something like this map (of receptor responses), but for metabolic regulation:

• Figure 1 - signal transduction - wikipedia

So it possibly contains mitochondria, O₂, CO₂, flows, ATP, NADPH, etc... I understand that different cell types can have different energy producer and consumer organelles and it is not possible to create something that is universally true, so I would be satisfied with a map of your favorite human cell type.

Answer 1

I heard somewhere that cells ………………………… so they regulate where they use up the energy.

Yes NADP/H is primarily employed in anabolic pathways such as fatty acid synthesis, while NAD/H is employed in catabolic pathways such as glycolysis.

I don't think there is a general rule for other "energy-currency" molecules (pyrimidine triphosphates are not used except in some rare cases such as glycogenesis).

I mean is there a simple map which contains the main processes and the energy carrier and regulatory compounds?

You can search for the term "metabolic network". It would be too huge so it is better to look at specific sub-networks. KEGG is a good site for finding metabolic networks. There are other representations like hive plots, to visualize very huge graphs.

Answer 2

Our body maintains a very delicate balance between the concentration of metabolites and substrates. If a pathway is not regulated, excess of a particular metabolite can disturb the whole process. Let's take cholesterol metabolism pathway for example. there are various means by which the cells control the production of cholesterol. For example AMP controlled kinase protein detects weather the concentration of ATP is high or not, if its low then the cell does not proceed with the production of it, by inhibiting the enzyme that catalysis the production of mevalonate. Other way is through transcription factor that is present called SREBP. Sterol Regulatory Element Binding Protein regulate multiple genes that are involved in metabolism of cholesterol. Various protein denaturing components are present that upon receiving signal cleaves the intermediate's in the metabolism of cholesterol. There are n-number of pathways in our body and all are regulated by a complex network of signals that regulate them.