Glycogenesis: Difference between revisions
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<StructureSection load=' | <StructureSection load='3rmv' size='350' side='right' scene='' caption='Human glycogenin-1 complex with UDP, ethanediol, Mg+2 (green) and Mn+2 (purple) ions (PDB code [[3rmv]])'> | ||
Glycogenesis is the process of glycogen synthesis, in which glucose molecules are added to chains of glycogen for storage. This process is activated during rest periods following the [[Cori cycle]], in the liver, and also activated by [[insulin]] in response to high glucose levels. | Glycogenesis is the process of glycogen synthesis, in which glucose molecules are added to chains of glycogen for storage. This process is activated during rest periods following the [[Cori cycle]], in the liver, and also activated by [[insulin]] in response to high glucose levels. | ||
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'''Step 4''' | '''Step 4''' | ||
The enzyme glycogenin is needed to create initial short glycogen chains, which are then lengthened and branched by the other enzymes of glycogenesis. Glycogenin, a homodimer, has a tyrosine residue on each subunit that serves as the anchor for the reducing end of glycogen. Initially, about seven UDP-glucose molecules are added to each tyrosine residue by glycogenin, forming α(1→4) bonds. | The enzyme [[glycogenin]] is needed to create initial short glycogen chains, which are then lengthened and branched by the other enzymes of glycogenesis. Glycogenin, a homodimer, has a tyrosine residue on each subunit that serves as the anchor for the reducing end of glycogen. Initially, about seven UDP-glucose molecules are added to each tyrosine residue by glycogenin, forming α(1→4) bonds. | ||
'''Step 5''' | |||
Once a chain of seven glucose monomers is formed, glycogen synthase binds to the growing glycogen chain and adds UDP-glucose to the 4-hydroxyl group of the glucosyl residue on the non-reducing end of the glycogen chain, forming more α(1→4) bonds in the process. | |||
'''Step 6''' | |||
Branches are made by glycogen branching enzyme (also known as amylo-α(1:4)→α(1:6)transglycosylase), which transfers the end of the chain onto an earlier part via α-1:6 glycosidic bond, forming branches, which further grow by addition of more α-1:4 glycosidic units | |||
</StructureSection> | </StructureSection> | ||
== References == | == References == | ||
<references/> | <references/> | ||
