Thiols Flashcards
Characteristics?
Sulfhydryl group Liquids Reducing agents Slightly soluble --> no H bonds with water Lower Thiols --> Toxic More acidic than alcohols
CH3Ch2-SH
Ethylmercaptan
CH3SH
Methylmercaptan
Name “Mercaptan”?
Mercaptan reaction with Mercuric salts
Affinity for Mercury
Toxicity of Heavy metals?
Blocking SH in the active sides of some enzymes
Oxidation products (Strong/Mild) ?
Mild: Alkyl Disulfides
Strong: Sulfinic / Sulfonic acid
Linking of a Polypeptide chain?
2 Residues of CystEine build Disulfide bonds –> CystIne residue as a Linkage
–> Resistant to Denaturation
Important Derivatives?
Mustard gas Dimercaprol Gluthathione Cysteamine Taurine Lipoid acid Allyl Disulfide
Mustard gas
Warfare agents
World war 1 –> Heavy oil liquid
Mustard gas medicine
Burns
Blindness
Death
Dimercaprol
British anti Lewisit
Antidote to Lewisite
Lewisite
Arsencial war gas
How do Arsenics react?
React with the SH containing molecules (e.g. in Tissues)
How does Dimercaprol fight Arsenics?
It competes with the SH Group from the Tissues for !! Arsenicals –> Forming a stable and relative non toxic chelat complex
Dimercaprol and Metals (that form mercaptides with essential cellular SH groups) ?
Antidote against poisoning —including arsenic, gold, lead, and mercury (that act by combining with cellular sulfhydryl groups)
GSH
- Tripeptide
- Antioxidant
- Isolated from yeast, muscle, and liver
Role in the respiration and protects red blood cells against hydrogen peroxide (Reducing it to Water) - Cofactor for various enzymes
- Formation of correct Disulfide Bonds in Proteins
- Intracellular reductant (Reducing agent) –> Maintain SH groups of enzymes in a reduced state
- Glutathione is not an essential nutrient for humans, since it can be synthesized in the body from the amino acids L-cysteine, L-glutamic acid, and glycine
Tripeptide
Compound composed of three amino acids
Linkage of GSH
Tripeptide with a gamma peptide linkage between the carboxyl group of the glutamate side chain and the amine group of cysteine, and the carboxyl group of cysteine is attached by normal peptide linkage to a glycine
Reducer
Substances that have the ability to reduce other substances (cause them to gain electrons)
Disulfide bridgen Biochemistry
A single covalent bond between the sulfur atoms to two amino acids called cysteine
Can be considered as part of the primary structure of a protein
They are very important in determining the tertiary + quaternary structure of proteins
What happens if GSH acts as a Reducing agent?
Its SH becomes oxidized and forms a disulfide ling with another GSH molecule
Cysteamine
Thio-ethanol-Amine
Constituent of CoA
SH Group is a carrier of acyl radicals in citric acid cycle …
How is CoA formed?
Activation of Panthothenic acid by Phosphorylation
Addition of Cystine
Adenylation by ATP
Cysteine Key Step in Metabolism?
Oxidation to Cysteinsulfinate
Decarboxlyation –> Hypotaurine
Hypotaurine is oxidized –> Taurine
