5Properties of amines:basicity of amines (the unshared pair of electrons on the nitrogen atom)form hydrogen bonds (the polarity of the carbon-nitrogen bond)form nitrosoamines (nitrites in food may cause cancer)nitrosoamine
6Importance of amines: The most important organic bases In biochemistry:Quaternary ammonium saltsBiogenic aminesAmino acidsProteinsAlkaloids
7Quaternary ammonium salts: Choline: Acetylcholine:- the constituent of phospholipids (lecithin) - neurotransmiter (parasympathetic nervous system)
8Acetylcholine- the transmitter of the parasympathetic and sympathetic system, at neuromuscular junctions, involved in learning and memory1. The synthesis: from choline and acetyl-CoA in the neurons2. Hydrolysis: in the synaptict cleft (restores the resting potential in the postsynaptic membrane)
9Biogenic amines: from amino acids by decarboxylation constituents of biomolecules, neurotransmittersAmino acidAmineFunctionSerineEthanolaminePhospholipidsCysteineThyoethanolamineComponent of coenzyme AThreonineAminopropanolComponent of vitamin B12Aspartateβ-AlanineGlutamateγ-AminobutyrateNeurotransmitter (GABA)HistidineHistamineMediator, neurotransmitterDopaDopamineNeurotransmitter5-hydroxytryptophanSerotonin
11Adrenaline and amphetamines: Catecholamines (adrenaline and noradrenaline)biogenic amines with catechol group derived from tyrosinehormones (the adrenal medulla), neurotransmitters (sympathetic nervous system)Amphetaminesmimic the action of catecholaminesstimulate the cortex (abuse)
13Opium and opiates: = morphine alkaloids important in medicine, abuse bind to the opioid receptorsExamples:Opium, morphine – analgetic, the immature seed pods of opium poppiesCodeine – analgetic, antitussiveHeroin – synthesizes from morphineSearch similar compounds(without addiction):
14Amides: R-CO-NH2an amino group or substituted amino group bonded to a carbonyl carbonProperties:not basic (the carbonyl group draws electrons away from the nitrogen)formation of the peptide bond –NH2 + HOOC- (enzyme-catalyzed)The great stability toward hydrolysis (the peptide bond is stable, enzymatic hydrolysis)
17Carbamate and urea Carbamoyl phosphate = carbonic acid amides (H2CO3) - intermediate in: urea cyclethe formation of pyrimidines
18Urea the end-product of protein metabolism in mammals produced only in the liver (urea cycle)soluble in water (excreted in the urine)electron delocalization → weak acidbiuret test (detection of peptide bonds and urea) - heating - biuret in alkaline environment with Cu2+ - purple
23Imines: R-C=N-R Schiff bases functional group that contains a carbon-nitrogen double bond with the nitrogen atom connected to an aryl or alkyl groupchargedMechanism of transamination:
24Sulfur compoundsStructurally similar to oxygen compound
25Thiols: R-SH (sulfhydryl group) Properties:Not form hydrogen bondsStronger acids than alcoholsEasily oxidized → disulfideExamples:Cystein
26Disulfides: R-S-S-R Disulfide-bonded cystein residues The disulfide bond forms when the two thiol groups are oxidized (reverse reaction)Protein conformation!
27GlutathioneAn antioxidant (elimination of H2O2 and organic hydroperoxides)Glutathione peroxidaseGlyCysGluGlyCysGluGlyCys SHGlu+ R-O-O-HS S+ H2O+ NADPHGlutathione reductaseReduced form of glutathione(monomer)Oxidized form of glutathione(dimer, disulphide)
28Sulfides: R-S-R Examples: Methionine S-Adenosylmethionine (SAM) = sulfonium ionHighly reactive methyl group (an important methylation agent)!