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www.ncbi.nlm.nih.gov/books/NBK22399

The covalent attachment of another molecule can modify the activity of enzymes and many other proteins. In these instances, a donor molecule provides a functional moiety that modifies the properties of the enzyme. Most modifications are reversible. Phosphorylation and dephosphorylation are the most common but not the only means of covalent modification.

en.wikibooks.org/.../Enzyme_Regulation/Reversible_covalent_modification

The acceptor is usually a serine, threonine, or tyrosine residue, amino acids that contain hydroxide. The process of the covalent modification may be reversible, but not in all cases. One common example of covalent regulation is protein phosphorylation.

www.khanacademy.org/.../enzyme-kinetics/v/covalent-modifications-to-enzymes

- [Voiceover] So today we're gonna learn about covalent modifications to enzymes. But first, let's review the idea that enzymes make reactions go faster. And looking at a reaction coordinate diagram you notice that enzymes do this by lowering the reaction's activation energy. Also, before we talk ...

alpha.chem.umb.edu/chemistry/biochm383/files/Notes_summer/regulation.pdf

Regulation of Enzyme Activity Manickam Sugumaran Professor of Biology U.Mass - Boston Boston, MA 02125 The Theme of This Lecture Regulation of Enzyme Activity at Protein Level. 1. Covalent modification. 2. Noncovalent (allosteric) regulation 3. Protein degradation (will not be considered).

en.wikipedia.org/wiki/Regulatory_enzyme

Here, the active and inactive form of the enzymes are altered due to covalent modification of their structures which is catalysed by other enzymes. This type of regulation consists of the addition or elimination of some molecules which can be attached to the enzyme protein.

www.cliffsnotes.com/.../biology/biochemistry-i/enzymes/covalent-modification

Many enzymes are activated or inactivated by the transfer of inorganic phosphate from ATP to an acceptor—for example, the side‐chain oxygen of serine. The combination of protein phosphorylation by kinases and dephosphorylyation by phosphatases can afford a fine level of control over enzyme ...

www.answers.com/Q/Difference_between_allosteric_and_covalent_modulation

The 2 mechanisms to alter protein shape are allosteric and covalent modulation. Allosteric: If the protein contains 2 binding sites, the noncovalent binding of a ligand to one site can alter the ...

www.reference.com/science/covalent-modification-50cdf04502942aea

Covalent modification is the alteration of a synthesized protein facilitated by a catalyst. The structure and function of the protein is modified, changing its role in cellular regulation. Covalent modifications involve the addition or removal of chemical groups on a protein and may involve a single or multiple amino acids.

en.wikipedia.org/wiki/Covalent_modulation

Post-translational modification (PTM) refers to the covalent and generally enzymatic modification of proteins following protein biosynthesis.Proteins are synthesized by ribosomes translating mRNA into polypeptide chains, which may then undergo PTM to form the mature protein product. PTMs are important components in cell signaling, as for example when prohormones are converted to hormones.

stiefkind.blogspot.com/2011/05/enzymes-regulation.html

Several types of regulation may occur in the same enzyme. Which enzyme in a pathway is usually the regulatory enzyme? It is usually the first one. This is a way to save energy, of course. Enzymes may be regulated by different mechanisms, such as : substrate level regulation, allosteric regulation and covalent regulation.