Biomaterial Database

Studies on the inhibition of proteolytic enzymes by serum. I. The mechanism of the inhibition of trypsin, plasmin, and chymotrypsin by serum using fibrin tagged with I131 as a substrate. 1952

N R SHULMAN

The mechanism of the inhibition of trypsin, plasmin, and chymotrypsin by serum was studied using fibrin tagged with radioactive iodine as a substrate. Enzyme-inhibitor relationships were studied by: (a) varying the concentration of serum; (b) varying the concentration of enzyme; and (c) by diluting the enzyme-serum mixture. The results indicate that the inhibition of trypsin, plasmin, and chymotrypsin is a stoichiometric and irreversible reaction. By using the Lineweaver-Burk graphical method of analysis it was demonstrated that the inhibition of trypsin and chymotrypsin is a non-competitive reaction. This finding supports the conclusion that inhibition by serum is an irreversible type of reaction. The substrate was found to exert a retarding effect on the activity of plasmin. The possibility of a plasmin inhibitor in fibrinogen was suggested. The suitability of the various procedures used in evaluating serum proteolytic inhibition was discussed.

UI	MeSH Term	Description	Entries
D010447	Peptide Hydrolases	Hydrolases that specifically cleave the peptide bonds found in PROTEINS and PEPTIDES. Examples of sub-subclasses for this group include EXOPEPTIDASES and ENDOPEPTIDASES.	Peptidase,Peptidases,Peptide Hydrolase,Protease,Proteases,Proteinase,Proteinases,Proteolytic Enzyme,Proteolytic Enzymes,Esteroproteases,Enzyme, Proteolytic,Hydrolase, Peptide
D010450	Endopeptidases	A subclass of PEPTIDE HYDROLASES that catalyze the internal cleavage of PEPTIDES or PROTEINS.	Endopeptidase,Peptide Peptidohydrolases
D002918	Chymotrypsin	A serine endopeptidase secreted by the pancreas as its zymogen, CHYMOTRYPSINOGEN and carried in the pancreatic juice to the duodenum where it is activated by TRYPSIN. It selectively cleaves aromatic amino acids on the carboxyl side.	Alpha-Chymotrypsin Choay,Alphacutanée,Avazyme
D005337	Fibrin	A protein derived from FIBRINOGEN in the presence of THROMBIN, which forms part of the blood clot.	Antithrombin I
D005340	Fibrinogen	Plasma glycoprotein clotted by thrombin, composed of a dimer of three non-identical pairs of polypeptide chains (alpha, beta, gamma) held together by disulfide bonds. Fibrinogen clotting is a sol-gel change involving complex molecular arrangements: whereas fibrinogen is cleaved by thrombin to form polypeptides A and B, the proteolytic action of other enzymes yields different fibrinogen degradation products.	Coagulation Factor I,Factor I,Blood Coagulation Factor I,gamma-Fibrinogen,Factor I, Coagulation,gamma Fibrinogen
D005341	Fibrinolysin	A product of the lysis of plasminogen (profibrinolysin) by PLASMINOGEN activators. It is composed of two polypeptide chains, light (B) and heavy (A), with a molecular weight of 75,000. It is the major proteolytic enzyme involved in blood clot retraction or the lysis of fibrin and quickly inactivated by antiplasmins.	Plasmin,Fibrogammin,Glu-Plasmin,Protease F,Thrombolysin,Glu Plasmin
D014357	Trypsin	A serine endopeptidase that is formed from TRYPSINOGEN in the pancreas. It is converted into its active form by ENTEROPEPTIDASE in the small intestine. It catalyzes hydrolysis of the carboxyl group of either arginine or lysine. EC 3.4.21.4.	Tripcellim,Trypure,beta-Trypsin,beta Trypsin