Amidation phosphate carriers

The third group is water-immiscible organic species with electron donor or acceptor properties, or solvating carriers. They include carbon-oxygen compounds (amides, ethers, ketones) phosphorus-oxygen compounds (tri- -butylphosphate (TBP), dibutyl-phosphate (DBP) or-phosphonate (DBBP) phosphine oxides (tri- -octylphosphine oxide (TOPO) phosphine sulfides (Cyanex 471) alkyl sulfides (dihexyl, diheptyl sulfides) nitrogen containing compounds (CLX 50), and so on [1-7, 81, 83]. All of them are known as selective extractants, but few of them are tested as carriers in LM processes. 

Amide bonds are found in many proteins. One is the acyl carrier protein of Escherichia coli (see 90), which contains the peptide backbone, and a 4 -phosphopantetheine unit (in violet in the illustration) is attached to a serine residue. Note the amine bonds in the pantothenic acid unit and also the 0-P=0 unit, which is a phosphate ester (an ester of phosphoric acid). An acyl carrier protein is involved in fatty acid synthesis, linking acetyl and malonyl groups from acetyl coenzyme A and malonyl coenzyme A to form P-keto acid acyl carrier protein (abbreviated as ACP). The widely utilized acetyl CoA is an ester (91) attached to coenzyme A. Acetyl CoA is a key intermediate in aerobic intermediary metabolism of carbohydrates, lipids, and some amino acids. 

Dolichol phosphate (Dol-P) is the carrier lipid involved in the assembly of oligosaccharides for transfer to the amide nitrogen of L-asparagine of proteins. The precursor oligosaccharide pyrophosphoryl dolichol is biosynthesized in the endoplasmic reticulum or in the Golgi bodies of eukaryotes from dolichol phosphate and nucleotide diphospho sugars, UDP-GlcNAc, GDP-Man, and UDP-Glc. 

Nicotinic amide, C H4N.CO.NH2, is a constituent of the coenzymes, co-dehydrase I and II, and as such acts as a hydrogen carrier in tissue respiration. The amide is derived from nicotinic acid, or carboxy pyridine, and is combined with ribose phosphate and adenosine in nucleotide structure in the co-dehydrases. Its hydrogen-carrying power is due to the reducibility of the onium nitrogen in the pyridine ring (p. 258). 

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