Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
 10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

MTX peptides in which the amino acid was linked to the alpha-carboxyl group have been prepared and examined for cytotoxicity before and after treatment with proteolytic enzymes. The alanine, aspartic acid and arginine derivatives (MTX-ala, MTX-asp and MTX-arg) were synthesized by a regio-specific route, following the general procedures of Rosowsky and Montgomery. Each compound was obtained in good yield, and purity was established by TLC, HPLC, absorbance spectra and elemental analyses. The MTX peptides were not hydrolyzed by a variety of proteolytic enzymes (e.g., trypsin, plasmin, urokinase, aminopeptidase). Pancreatic carboxypeptidase A, however, hydrolyzed MTX-ala readily, MTX-asp slowly and MTX-arg not at all. The MTX-ala and, to a lesser extent, MTX-arg were substrates for pancreatic carboxypeptidase B. MTX-arg was also hydrolyzed by the endogenous carboxypeptidase N in human serum. The cytotoxicity of these MTX peptides toward L1210 cells was measured in a microculture assay system using a tetrazolium dye. MTX-ala was weakly cytotoxic (ID50 = 2.0 x 10(-6)M) compared to MTX (ID50 = 2.4 x 10(-8)M). When MTX-ala was tested in the presence of carboxypeptidase A, the ID50 value improved to 8.5 x 10(-8)M. MTX-arg gave an ID50 of 5.0 x 10(-8)M, which was not unexpected in view of its susceptibility to hydrolysis by the carboxypeptidase activity present in the fetal calf serum of the culture medium. Inclusion of carboxypeptidase B lowered the ID50 value to 2.5 x 10(-8)M. Possible clinical uses of MTX peptides are discussed.
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PMID:Chemotherapeutic potential of methotrexate peptides. 307 29

Zymogen activation is an important biochemical control process and has important physiological and pathological implications. We have simultaneously measured both procarboxypeptidase A, the enzyme precursor, and carboxypeptidase A, its active product, in serum by using an affinity resin and the synthetic peptide substrate N-(2-furanacryloyl)-L-phenylalanyl-L-phenylalanine. Serum procarboxypeptidase A is activated by trypsin, chymotrypsin, plasmin, subtilisin, or urokinase but not by thrombin or enteropeptidase. The molecular weight of the precursor is approximately 5000-10 000 greater than that of the active product. Both enzyme and precursor increase in serum in the course of pancreatic inflammation, but the degree of activation can vary up to 2000-fold, independent of the amount of precursor present. The existence of this pancreatic proteolytic precursor in serum opens new avenues for the investigation of zymogen activation and its regulation.
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PMID:Human serum procarboxypeptidase A. 634 78

The complete sequence of 157 amino acids of the light (A) chain of high molecular mass urokinase from human urine was determined. The fragmentation strategy included cyanogen bromide cleavage of the S-carboxymethylated A chain at the methionine and/or tryptophan residues and use of the specific endoproteinase Lys-C. For sequence determination automated solid- or liquid-phase techniques of Edman degradation were used. C-terminal amino acids of the A chain were determined by consecutive treatment with carboxypeptidase A and B. The amino acid sequence obtained revealed a significant homology to peptide chains of other serine proteinases. Accordingly, the sequence of the A chain can be divided into three domains: 1) The growth factor domain with homologies to murine epidermal growth factor and a particular sequence of bovine clotting factor X, 2) The "kringle" domain with homologies to "kringle" structures, e.g. in plasminogen, and 3) the connecting peptide domain containing the A1 chain of low molecular mass urokinase. Together with the amino acid sequence of the B chain, which was presented by us in an earlier communication, the sequence data presented complete the primary structure of high molecular mass urokinase from human urine.
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PMID:The primary structure of high molecular mass urokinase from human urine. The complete amino acid sequence of the A chain. 675 69