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Related Concept Videos

Phase II Reactions: Sulfation and Conjugation with α-Amino Acids01:19

Phase II Reactions: Sulfation and Conjugation with α-Amino Acids

Sulfation and α-amino acid conjugation are two critical biotransformation reactions in drug metabolism. Sulfation, a phase II biotransformation reaction, involves adding a polar sulfate group to a drug, enhancing its water solubility and promoting excretion. This process can either co-occur with or occur independently of glucuronidation. Nonmicrosomal sulfotransferase enzymes catalyze the process. The reaction involves 3'-phosphoadenosine-5'-phosphosulfate or PAPS coenzyme activation, sulfur...
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Protein Modifications in the RER

Modification of secretory and transmembrane proteins entering the rough ER begins in the ER lumen. These modifications aid in protein folding and stabilize the acquired tertiary structure. Protein modifications in the rough ER co-occur at different stages of protein folding.
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.
Drug Metabolism: Phase II Reactions01:14

Drug Metabolism: Phase II Reactions

Phase II reactions are essential for the detoxification and elimination of drugs from the body. These reactions involve the conjugation of parent drugs or their phase I metabolites with endogenous molecules, resulting in more hydrophilic drug conjugates. The primary conjugation reactions in this phase are sulfation and glucuronidation. Both sulfation and glucuronidation typically produce biologically inactive metabolites. However, in some cases involving prodrugs, active metabolites may be...
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Protein glycosylation starts in the ER lumen and continues in the Golgi apparatus. Glycosyltransferases catalyze the addition of sugar molecules or glycosylation of proteins. Usually, these enzymes add sugars to the hydroxyl groups of selected serine or threonine residues to form O-linked glycans or the amino groups of asparagine residues to form N-linked glycans. Different positions on the same polypeptide chain can contain differently linked glycans.
Multiple sugar molecules that may or may...
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Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase

Phase II biotransformation reactions are essential for detoxifying and eliminating xenobiotics, including many pharmaceutical compounds. These reactions typically involve conjugation, the covalent attachment of polar endogenous groups such as glucuronic acid, sulfate, methyl, or acetyl moieties to functional groups introduced during Phase I metabolism. The resulting conjugates are more water-soluble, enabling efficient renal or biliary excretion.The major classes of Phase II enzymes include...
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Engineering sulfotransferases to modify heparan sulfate.

Ding Xu1, Andrea F Moon, Danyin Song

  • 1Division of Medicinal Chemistry and Natural Products, School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, USA.

Nature Chemical Biology
|January 29, 2008
PubMed
Summary

Researchers engineered heparan sulfate (HS) 3-O-sulfotransferase enzymes by altering key amino acid residues. This modification successfully changed enzyme substrate specificity, enabling tailored modification of HS for specific functions.

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Area of Science:

  • Biochemistry
  • Glycobiology
  • Enzyme Engineering

Background:

  • Heparan sulfate (HS) biosynthesis relies on diverse sulfotransferases.
  • Understanding HS biosynthesis is crucial for developing targeted therapeutics.
  • HS 3-O-sulfotransferase isoforms play critical roles in HS modification.

Purpose of the Study:

  • To engineer the substrate specificity of heparan sulfate (HS) 3-O-sulfotransferase isoforms.
  • To investigate the role of specific amino acid residues in HS sulfotransferase substrate selection.
  • To demonstrate the potential for tailoring HS structure and function through enzyme engineering.

Main Methods:

  • Utilized crystal structures of HS 3-O-sulfotransferases to identify key residues.
  • Performed site-directed mutagenesis on identified amino acid residues.
  • Assessed the impact of mutations on enzyme substrate specificity.

Main Results:

  • Identified a specific pair of amino acid residues crucial for substrate selection in HS 3-O-sulfotransferases.
  • Mutations in these residues resulted in altered substrate specificities.
  • Demonstrated successful engineering of HS sulfotransferase specificity.

Conclusions:

  • The substrate specificity of HS 3-O-sulfotransferases can be effectively engineered.
  • Targeted modification of HS biosynthesis is achievable through enzyme engineering.
  • This approach holds promise for developing novel HS-based functional materials and therapeutics.