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)

On storage at 4 degrees C, rabbit skeletal muscle AMP deaminase undergoes limited proteolysis with the conversion of the native 85-kDa enzyme subunit to a 75-kDa core that is resistant to further proteolysis. Further studies have shown that limited proteolysis of AMP deaminase with trypsin, removing the 95-residue N-terminal fragment, converts the native enzyme to a species that exhibits hyperbolic kinetics even at low K+ concentration. The results of this report show that a 21-residue synthetic peptide, when incubated with the purified enzyme, is cleaved with a specificity identical to that reported for ubiquitous calpains. In addition, the cleavage of a specific fluorogenic peptide substrate by rabbit m-calpain is inhibited by a synthetic peptide that corresponds to residues 10-17 of rabbit skeletal muscle AMP deaminase; this peptide contains a sequence (K-E-L-D-D-A) that is present in the fourth subdomain A of rabbit calpastatin, suggesting that the N-terminus of AMP deaminase shares with calpastatin a regulatory sequence that might exert a protective role against the fragmentation-induced activation of AMP deaminase. These observations suggest that a calpain-like proteinase present in muscle removes from AMP deaminase a domain that holds the enzyme in an inactive conformation and which also contains a regulatory region that protects against unregulated proteolysis. We conclude that proteolysis of AMP deaminase is the basis of the large ammonia accumulation that occurs in skeletal muscle subjected to strong tetanic contraction or passing into rigor mortis.
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PMID:A calpain-like proteolytic activity produces the limited cleavage at the N-terminal regulatory domain of rabbit skeletal muscle AMP deaminase: evidence of a protective molecular mechanism. 1548 71

Identification of peptide substrates for proteases can be a major undertaking. To overcome issues such as feasibility and deconvolution, associated with large peptide libraries, a 'small but smart' generic fluorescence resonance energy transfer rapid endopeptidase profiling library (REPLi) was synthesised as a tool for rapidly identifying protease substrates. Within a tripeptide core, flanked by Gly residues, similar amino acids were paired giving rise to a relatively small library of 3375 peptides divided into 512 distinct pools each containing only 8 peptides. The REPLi was validated with trypsin, pepsin, the matrix metalloprotease (MMP)-12 and MMP-13 and calpains-1 and -2. In the case of calpain-2, a single iteration step involving LC-MS, provided the definitive residue specificity from which a highly sensitive fluorogenic substrate, (FAM)-Gly-Gly-Gly-Gln-Leu-Tyr-Gly-Gly-DPA-Arg-Arg-Lys-(TAMRA), was then designed. The thorough validation of this 'small but smart' peptide library with representatives from each of the four mechanistic protease classes indicates that the REPLi will be useful for the rapid identification of substrates for multiple proteases.
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PMID:A broad-spectrum fluorescence-based peptide library for the rapid identification of protease substrates. 1647 34


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