Protein trypsinogen

Figure 6 Separation of basic proteins on an untreated fused silica capillary with diaminopropane as buffer additive. Capillary 75 cm (55 cm to detector) x 50 p i.d. Buffer pHs are as noted on the figure with 30 to 60 mM DAP as an additive 200 to 240 V/cm peak identification 1 = lysozyme, 2 = cytochrome, 3 = ribonuclease, 4 = a-chymotrypsin 5 = trypsinogen, 6 = r-huIL-4. (From Bullock, J. A. and Yuan, L.-C., /. Microcol. Sep., 3, 241, 1991. With permission.)...

Kenner, R. A. and Aboderin, A. A. (1971). A new fluorescent probe for protein and nucleoprotein conformation. Binding of 7-(p-Methoxyben-zylamino) -4-nitrobenzoxadiazole to bovine trypsinogen and bacterial ribosomes. Biochemistry 10, 4433 1440. 

Proteolysis cleavage of peptide bonds to remodel proteins and activate them (ptoin-sulin, trypsinogen, prothrombinj... 

Protein digestion occurs in two stages endopeptidases catalyse the hydrolysis of peptide bonds within the protein molecule to form peptides, and the peptides are hydrolysed to form the amino acids by exopeptidases and dipeptidases. Enteropeptidase initiates pro-enzyme activation in the small intestine by catalysing the conversion of trypsinogen into trypsin. Trypsin is able to achieve further activation of trypsinogen, i.e. an autocatalytic process, and also activates chymotrypsinogen and pro-elastase, by the selective hydro-... 

Antitrypsin Blood and other body fluids contain a protein, ai -antitrypsin (ai-AT, currently also called ai-aritiproteinase), that inhibits a number of proteolytic enzymes (also called proteases or proteinases) that hydrolyze and destroy proteins. [Note The inhibitor was originally named oti-antitrypsin because it inhibits the activity of trypsin (a proteolytic enzyme synthesized as trypsinogen... 

In trypsinogen, a region of the protein at the binding pocket is disordered, indicating conformational flexibility.133,134 On activation or on the addition of a small peptide that can bind to the buried Asp-194, this region takes on a well-defined structure. 

The inactive precursors are called trypsinogen, pepsinogen, chymotrypsino-gen, and procarboxypeptidase. These precursors are converted to the active enzymes by hydrolytic cleavage of a few specific peptide bonds under the influence of other enzymes (trypsin, for example, converts chymotrypsinogen to chymotrypsin). The digestive enzymes do not appear to self-destruct, probably because they are so constructed that it is sterically impossible to fit a part of one enzyme molecule into the active site of another. In this connection, it is significant that chymotrypsin attacks denatured proteins more rapidly than natural proteins with their compact structures of precisely folded chains. 

Figure B3.1.1 A 15% SDS-polyacrylamide gel stained with Coomassie brilliant blue. Protein samples were assayed for the purification of a proteinase, cathepsin L, from fish muscle according to the method of Seymour et al. (1994). Lane 1, purified cathepsin L after butyl-Sepharose chromatography. Lane 2, cathepsin L complex with a cystatin-like proteinase inhibitor after butyl-Sepharose chromatography. Lane 3, sarcoplasmic fish muscle extract after heat treatment and ammonium sulfate precipitation. Lane 4, sarcoplasmic fish muscle extract. Lanes M, low-molecular-weight standards aprotinin (Mr 6,500), a-lactalbumin (Mr 14,200), trypsin inhibitor (Mr 20,000), trypsinogen (Mr 24,000), carbonic anhydrase (Mr 29,000), gylceraldehyde-3-phosphate dehydrogenase (Mr 36,000), ovalbumin (Mr 45,000), and albumin (Mr 66,000) in order shown from bottom of gel. Lane 1 contains 4 pg protein lanes 2 to 4 each contain 7 pg protein.

Human pancreatic secretory trypsin inhibitor (hPSTI) can be potentially assayed as an indicator of necrotic complications in AP (Ol). This protein is an inhibitor of trypsinogen, which is produced in acinar cells in the quantity of approximately 2% of the potential content of trypsin in pancreas. Trypsin binds with its inhibitor hPSTI, then with AMG, and only this complex, trypsin-o 2-macroglobulin, is eliminated from plasma (B10). Pezzili (P3) suggests that early attempts to determine the severity of the AP process based on the measurement of hPSTI within 24 hr from the first sensations of pain show a sensitivity of 79%, whereas an increase in CRP concentration has a sensitivity of 29% only (Table 3). 

For trypsinogen activation, enteropeptidase (enterokinase, EC 3.4.21.9) [23] is a key enzyme for mammalian protein digestion. The selective cleavage site of trypsinogen by enteropeptidase initiates Lys6-Ile7 bond. Then trypsin (EC 3.4.21.4) activates other zymogens. Thus, the formation of trypsin by enteropeptidase is the master activation step. 

Hydrolyses proteins with broad specificity. Generally favours hydrophobic residues in Pi and Pi but accept Lys in Pj, which leads to activation of trypsinogen. Does not clot milk. 

FIGURE 13 Plot of the logarithm of the retention volume (In VR) versus the concentration of the displacing salt, ammonium sulphate, in the HP-HIC mode with the proteins I, insulin B-chain 2, bovine trypsin inhibitor 3, bovine trypsinogen 4, insulin A-chain 5, ribonuclease 6, sperm whale myoglobin 7, horse heart cytochrome c. Data from Ref. 42. 

---