Hemoglobin exhibits positive cooperativity. Glyceraldehyde-3-phosphate dehydroge

Question

Hemoglobin exhibits positive cooperativity. Glyceraldehyde-3-phosphate dehydrogenase, however, exhibits negative cooperativity. Please explain how glyceraldehyde-3-phosphate dehydrogenase would bind to multiple substrates. Hemoglobin exhibits positive cooperativity. Glyceraldehyde-3-phosphate dehydrogenase, however, exhibits negative cooperativity. Please explain how glyceraldehyde-3-phosphate dehydrogenase would bind to multiple substrates. Hemoglobin exhibits positive cooperativity. Glyceraldehyde-3-phosphate dehydrogenase, however, exhibits negative cooperativity. Please explain how glyceraldehyde-3-phosphate dehydrogenase would bind to multiple substrates.

Explanation / Answer

Cooperativity is a phenomenon in which identical or near-identical elements are considered in a system, and these elements depend on each other for their functions relative to a hypothetical system where the elements function independently and individually. Now cooperativity can be positive or negative. If the function, say for example the affinity of a molecule to a substrate's binding sites, is enhanced by one molecule being attached, that makes way for other similar molecules to attach too. Like in the case of hemoglobin, one oxygen atom binds at one binding site out of the four of hemoglobin increasing the chances of more oxygen atoms to get attached to the remaining three binding sites. The contrast is true for negative cooperativity like in GAPDH.

Talking about GAPDH, it is a very crucial enzyme that acts in the sixth step of glycolysis and thus helps break down the glucose into energy. A study reveals that it has 3 anion binding sites. 'Ps' that binds to the C3 phosphate of the substrate. 'Pi' and 'New Pi' for inorganic phosphate.

GAPDH is also known to participate in many more reactions and processes.

Protein-Protein interactions

It can attach to tubulin, transferrin, actin and can also self-associate into homotypic oligomers.

Nucleic acid interactions

GAPDH binds to single-stranded RNA and DNA and also to a number of nucleic acids like tRNA, telomeric DNA, Hepatitis Viral RNA etc.

GAPDH is also known to bind inhibitors like Koningic acid

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