Trypsin inhibitor pancreatic, molecular weight

Figure 2. SDS gel electrophoresis of the products of partial cystine cleavage for several test proteins. A. molecular weight standards, B. yeast alcohol dehydrogenase. C. P-lactoglobulin, D. hen egg lysozyme, E. ovalbumin, F. calf fetal serum fetuin. Molecular weight standards are indicated by arrows on the left side of the gel and are bovine serum albumin (66,300), bovine liver glutamate dehydrogenase (55,400), porcine muscle lactate ddiydiogenase (36,500), bovine erythrocyte carbonic anhydrase (31,000), soybean trypsin inhibitor (21,500), hen egg lysozyme (14,400), bovine lung aprotinin (6,000), unresolved bovine pancreatic insulin A and B chains.

Protein (arginine) methyltransf erase has been purified approximately 34-fold from calf thymus (202). The enzyme has a pH optimum of 7.4 and a Km of 2.1 X 10 6M for S-adenosyl-L-methionine, which is at least 100 times lower than the in vivo level of this co-factor. The enzyme may have a molecular weight as high as 1-2 million (206). Although myelin protein is the best substrate for the enzyme (207), it has ben shown to methylate various histones, bovine serum y-globulin, trypsin inhibitor, and pancreatic ribonuclease (208). 

There appears to be sequence homology between the pineapple stem bromelain inhibitors and some of the small molecular weight inhibitors from the legumlnosae (91) Human inter-a-trypsin inhibitor contains two domains with great similarity to the domains of the Kunitz-type inhibitors (44 92-94)> The ovoinhibitors from Japanese quail and chicken egg whites contain six tandem domains which are homologous to the Kazal pancreatic secretory inhibitor and to the ovomucoids (69) ... 

Fig. 3.13. Proportionality of the loss of accessible surface area to the molecular weight of proteins (from Janin, 1976). Different proteins insulin, rubredoxin, pancreatic trypsin inhibitor, HIPIP, calcium binding protein, ribonuclease S, lysozyme, staphylococcal nuclease, papain, chymotrypsin, concanavalin A, subtilisin, thermolysin, carboxypeptidase A.

The formation of tertiary structure buries a certain amount of secondary structure surfaces which varies from 32% to 60%. The proportion of the surface which is buried varies for each protein and increases with the molecular weight of the protein. In fact, it is the proportion of the nonpolar surface that becomes buried during folding, which increases with the molecular weight. From 60% for pancreatic trypsin inhibitor, it varies up to 79% in carboxypeptidase among the six proteins considered by Chothia... 

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