Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The substrate specificity of proteinase B (EC 3.4.22.9) from Baker's yeast was studied. Experiments with unblocked synthetic peptides indicated that the enzyme has no aminopeptidase activity. The proteinase cleaves trypsin substrates like Bz-Arg-OEt, Bz-Arg-pNA and Bz-Ile-Glu-Gly-Arg-pNA and chymotrypsin substrates like Ac-Tyr-OEt and Bz-Tyr-pNA. The Km value for Ac-Tyr-OEt is similar to that of chymotrypsin A, but the catalytic activity per mol proteinase B amounts to only 1/20 that of chymotrypsin A. Km and kcat for Bz-Arg-OEt are 1/50 and 1/7 as high as the corresponding values determined for trypsin. Proteinase B cleaved the oxidized insulin B chain with an initial rapid cleavage step at Leu(15)-Tyr(16) and Phe(24)-Phe(25). Slower hydrolysis was observed at Gln(4)-His(5), Leu(11)-Val(12) Tyr(16)-Leu(17), Leu(17)-Val(18), Arg(22)-Gly(23) and Phe(25)-Tyr(26). These results suggest that the specificity of proteinase B is comparable to the specificity of porcine chymotrypsin C as well as of trypsin. When the hexapeptide Leu-Trp-Met-Arg-Phe-Ala was used as a substrate for proteinase B, the enzyme preferentially attacked at Arg-Phe and more slowly at Trp-Met.
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PMID:The substrate specificity of proteinase B from baker's yeast. 702 21

A number of inhibitors with different specificities were used to probe the involvement of proteinases in the mechanism of cytotoxic T lymphocyte (CTL)-mediated lysis. N-Acetyl-L-tyrosine ethyl ester (ATEE) and N-benzoyl-L-arginine ethyl ester (BAEE) are reversible substrate inhibitors of proteinases with trypsin-like and chymotrypsin-like specificities, respectively. BAEE did not prevent either the chromium release or DNA fragmentation induced in mouse tumor target cells by a mixed lymphocyte population. In contrast, ATEE inhibited both processes. The irreversible proteinase inhibitor 3,4-dichloroisocoumarin (DCI) also blocked both chromium release and DNA fragmentation, but at significantly lower concentrations than ATEE. More importantly, chromium release was more susceptible to inhibition by DCI than DNA fragmentation. Addition of a combination of the endonuclease inhibitor aurintricarboxylic acid plus DCI resulted in virtually complete inhibition of both DNA fragmentation and chromium release when the drugs were added at the beginning of the incubation period. In contrast addition of DCI 15 or 30 min following initiation of the lytic cycle abolished the affect of DCI on fragmentation, but not lysis. A model which suggests a dual role for the proteinases in CTL-mediated target cell death is presented. First, proteinases are involved in the initiation of DNA fragmentation. Second, they have an ongoing function in membrane damage.
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PMID:Proteinases are involved in both DNA fragmentation and membrane damage during CTL-mediated target cell killing. 773 79