Proteolytic digestion, partial

Sequence information can be obtained for peptides with molecular weights up to 2500 Da. Collision-induced dissociation of larger peptides reveal at least partial sequence information that will often suffice to solve a particular problem. The collision-induced dissociation method has been particularly useful on peptides from proteolytic digests, from which MS/MS data on different peptides can help identify the structure of a digested protein. 

Sato, K., Nakamura, M., Nishiya, T., Kawanari, M., and Nakajima, I. 1995. Preparation of a gel of partially heat-denatured whey protein by proteolytic digestion. Milchwissenschaft 50, 389-392. 

On fractionation on starch columns of a partial proteolytic digest such as that described above a peptide fraction was isolated containing aspartic... 

Partial proteolytic digestion provides quick information. However, because the sensitivity of a protein as opposed to proteases strongly depends on its conformation, this information is only dependable if both samples are completely denatured during the digestion and contain sufficient SDS (> 0.05%) (Walker and Anderson 1985). 

The values of the molecular weights calculated from the primary structures of Torpede a, B, y and a subunits from the nucleotide sequences of cloned cDNA [27, 28] are about 20% higher than those obtained by us from SEC/LALLS. We cannot clearly explain the discrepancy. However, as pointed out by Noda et al. [27], it is likely that a carboxy-terminal peptide is eliminated by post-transitional cleavage. Furthermore, we cannot entirely eliminate the possibility that partial proteolytic digestions may occur in the process of preparation of the receptor proteins. 

As shown in Table I, free HRP is poorly transported across MDCK cells but, when conjugated to a PLL carrier, HRP transport is increased considerably. The existence of a proteolytic compartment involved in the transcytotic digestion of HRP-S-PLL conjugate was further confirmed by the finding that when PLL was replaced by PDL, the transport of HRP was completely abolished (Table I) (8). In addition, when protease inhibitors such as leupeptin were added to the basal medium, the transcytosis of HRP was also significantly decreased (Table I). We have previously reported that the partial degradation of HRP-S-PLL was not inhibited by lysosomotropic amines (<8), indicating that this proteolytic process does not occur in lysosomes. 

In some instances there is a possibility that the efficacy of these preparations may be compromised by conditions associated with the digestive tract. Most function at pH values approaching neutrality. They would thus display activity possibly in saliva and particularly in the small intestine. However, the acidic conditions of the stomach (where the pH can be below 1.5) may denature some of these enzymes. Furthermore, the ingested enzymes would also be exposed to endogenous proteolytic activities associated with the stomach and small intestine. Some of these difficulties, however, may be at least partially overcome by formulating the product as a tablet coated with an acid-resistant film to protect the enzyme as it passes through the stomach. 

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