Carbohydrates peptide bond cleavage

Recently, the utilization of mercaptoethanesulfonic acid (299) as catalyst for hydrolysis of proteins was found to give very high tryptophan recoveries the results indicate improvement on the methods of Matsubara and Sasaki 249) and Liu and Chang 234). The acid has been used at a concentration of 3 N and hydrolysis time of 22 hrs at a temperature of 110°C are sufficient to give complete hydrolysis of protein molecules. Under these conditions, total cleavage of the highly resistant valine and isoleucine peptide bonds has also been obtained. However, if the protein sample contains carbohydrates, the... 

Human TNF-a is initially synthesized as a 233 amino acid polypeptide that is anchored in the plasma membrane by a single membrane-spanning sequence. This TNF pro-peptide, which itself displays biological activity, is usually proteolytically processed by a specific extracellular metallo-protease. Proteolytic cleavage occurs between residues 76 (Ala) and 77 (Val), yielding the mature (soluble) 157 amino acid TNF-a polypeptide. Mature human TNF-a appears to be devoid of a carbohydrate component, and contains a single disulfide bond. 

Kunz and Pfrengle [96] introduced the formation of a-amino-acid derivatives by U-4CR with chiral O-acylated amino-carbohydrates like 2i and formic acid 3f. Usually, their products are formed relatively stereoselectively, and generally in good yield. It seems that the use of formic acid 3f proceeds in the U-4CRs better than do other acid components of 3A, as its amine components like 2i are sterically hindered. The essential disadvantage of the products 18p is that subsequent cleavage of its C-N bond into 33 and 34 can be accomplished only by strong acids such as HC1. Thus, it is doubtful if delicate chiral a-amino acid derivatives or peptides can be prepared successfully in this manner. 

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