Acylated amino acids acyl chain length

Carboxypeptidase A is an exopeptidase which specifically hydrolyzes C-ter-minal aromatic and branched chain aliphatic amino acids from di- and polypeptides. Dipeptides in which the N-terminal amino group is free are hydrolyzed only slowly, whereas the corresponding N-acylated dipeptides are rapidly hydrolyzed. The presence of an N-methyl group on the a-amino nitrogen of either the first, or the second amino acid residue of a polypeptide greatly suppresses the rate of hydrolysis 33, 34). Hanson and Smith 143) and Abramowitz et al. 144) have shown that the identity of the side chain residue in polypeptides of up to five amino acid residues in length influences the magnitudes of ifm and cat-... 

Amino acid source Acyl chain length Surface tension y (mN m ) cmc r (mM) (10 mol/cm ) Krafft A (area (A )/ point molecule) (°C) ... 

There are instances of acylation by fatty acids with chain lengths other than 14 or 16 carbon atoms. One nutritionally important example is the recently identified orexigenic peptide ghrelin. The active form of this 28-amino-acid peptide hormone has the medium-chain fatty acid 8 0 covalently ester-ified to the hydroxyl group of serine-3. Octanoy-lated ghrelin is believed to act at the level of the hypothalamus to stimulate appetite, perhaps via neuropeptide Y. 

The acyl-Co A dehydrogenases are a family of mitochondrial flavoenzymes involved in fatty acid and branched chain amino-acid metabolism. In addition to long chain acyl-Co A dehydrogenases (LCADs), there are short/ branched chain acyl-CoA dehydrogenase (SBCAD) that act on 2-methyl branched chain acyl-CoA substrates of varying chain lengths. 

The length of tRe side chain R is important both for the quality and for the intensity of taste (Table V). Up to R=Et, D- and L-amino acids are sweet. R > Et causes bitter taste of increasing intensity in the L-series and increasing sweet taste in the D-se-ries. N-Acylation or esterification abolishes the sweet taste but increases the bitter taste (Table VI). 

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