Allosteric Enzyme Regulation and Covalent Enzyme modification
To discuss Allosteric Enzyme Regulation and Covalent Enzyme modification, we should know that both reversible and irreversible covalent enzyme alteration plays a major role in enzyme function regulation.
Enzyme Regulation – Allosteric Enzyme Regulation and Covalent modification is the topic of our this post. You would learn what is enzyme regulation and Allosteric Enzyme Regulation and Covalent modification.
A regulatory enzyme is an enzyme in a biochemical pathway which through its responses to certain signals, regulates the pathway’s activity.
For example- In cellular metabolism, groups of enzymes work together in sequential pathways to carry out a given metabolic process. The activities of metabolic pathways in cells are regulated by control of the activities of regulatory enzymes.
Regulation of Enzyme Activity:
- Allosteric regulation
- Covalent modification
- Proteolytic cleavage of a proenzyme
We only discuss the Allosteric regulation and Covalent modification in this Post.
Allosteric regulations the regulation of activities of an enzyme or a protein caused by the binding of modulators ( or effectors) at the site other than the active site of the enzyme or protein. There are two effects of Allosteric regulations and two effectors are may be available for the effects-
- feed-forward activators or
- feedback inhibitors
when a positive modulator is attached to the Enzyme then the enzyme becomes more active and when the Enzyme attached with the negative modulator then the enzyme becomes less reactive.
Covalent Enzyme Regulation:
Reversible covalent modification: In metabolic control, modulation of enzyme activity by attaching or releasing tiny groups plays a very significant role. The phosphorylation of particular serine, threonine or tyrosine groups is probably the most universal, and definitely the most well understood.
Irreversible covalent modification: Specific peptide bonds are often used for proteolytic cleavage to activate enzymes. Since proteolysis is essentially irreversible, turning the activity off requires another mechanism, often binding of inhibitory proteins.
Reversible Covalent Modifications:
- Reversible covalent modifications require an expenditure of energy and are often used in signaling from extracellular messages.
- In contrast, noncovalent interactions are reversible with no metabolic energy expended and sense conditions within a cell.
- Reversible covalent changes known to change the activity of the enzyme include:
- Phosphorylation of serine, threonine or tyrosine and less frequently aspartate and histidine residues.
- Acetylation of lysine or amino-terminal groups.
- Methylation of glutamate or aspartate residues
- Nucleotidylation of tyrosine residues
- ADP ribosylation primarily of arginine residues.
For example, we discuss the Phosphorylation and Dephosphorylation –
Phosphorylation and Dephosphorylation
- A family of enzymes called protein kinases that use adenosine triphosphate (ATP) as a donor of phosphate catalyzes phosphorylation processes.
- Phosphate groups are cleaved from phosphorylated enzymes by the action of phosphoprotein phosphatases
- The objectives for phosphorylation are amino acids with –OH groups.
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