Protein, acetylated phenolic groups

There is some evidence (Miller, 169 Ross and Tracy, 174) that the acetylated phenol groups of proteins are hydrolysed on long standing, even in nearly neutral solutions. Boor and Milln (175) have reported that... 

The immunologically specific substance characteristic of Group C Meningococcus has already been mentioned this was extracted from phenol-killed organisms, and protein was removed by the Sevag method after fractionation with ethanol, nucleic acid was removed as the copper salt. The product contained 5 % of nitrogen and 11 % of acetyl, and hexosamine was the only constituent other than sialic acid. ... 

There are two catecholate siderophores which may be chosen as model compounds for synthesis the cyclic enterobactin and the linear parabactin precursor N. N8-bis(2,3-dihydroxybenzoyl)spermidine. Both of these natural products are capable of the rapid removal of iron from transferrin, the human iron transport protein 89-90). The synthesis of these and other catecholate ligands routinely requires protection of the phenolic oxygens (for example, by methyl, benzyl or acetyl groups). Very few preparations of catechol-containing siderophores have appeared in which the unprotected 2,3-dihydroxybenzoyl group is used in the synthesis 91,92). 

Our laboratory has studied the stereochemistry of methyl group formation in a number of a, 0 elimination reactions of amino acids catalyzed by pyridoxal phosphate enzymes. The reactions include the conversions of L-serine to pyruvate with tryptophan synthase 02 protein (78) and tryptophanase (79), of L-serine and l-tyrosine with tyrosine phenol-lyase (80), and l-cystine with S-alkylcysteine lyase (81). In the latter study, the stereospecific isotopically labeled L-cystines were obtained enzymatically by incubation of L-serines appropriately labeled in the 3-position with the enzyme O-acetyl serine sulfhy-drase (82). The serines tritiated in the 3-position were prepared enzymatically starting from [l-3H]glucose and [l-3H]mannose by a sequence of reactions of known stereochemistry (81). The cysteines were then incubated with 5-alkyl-cysteine lyase in 2H20 as outlined in Scheme 19. The pyruvate was trapped as lactate, which was oxidized with K2Cr202 to acetate for analysis. Similarly, Cheung and Walsh (71) examined the conversion of D-serine to pyruvate with... 

N-Acetylimidazole (NAI) is a specific modifier of tyrosine residues. NAI acetylates the phenolic hydroxyl group in a reversible reaction, which reduced the absorption of enzyme at250-300 nm, especially at 278nm [122,123],Modification of tyrosine residues by NAI showed that tyrosine residue was essential for CCBE s chitosanase activity, but not involved in its CMCase catalysis.While the sharp decrease of both activities of CCBE by Ch-T were resulted from the crack of protein. In conclusion, the modified residues were all detected by activity and kinetic analysis. Ultra Voilet Spectroscopy, fluorescence, ative/SDS-PAGE and Circular Dichroism (CD) analysis. 

---