Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat forebrain Ca(2+)/calmodulin-dependent protein kinase II (CaM-kinase II) in isolated postsynaptic densities (PSD) was subjected to limited proteolysis with chymotrypsin or mu-calpain, a Ca(2+)-dependent protease. Incubation of the kinase with either protease resulted in a three- to fivefold enhancement of total kinase activity and solubilization of Ca(2+)/calmodulin (CaM)-independent activity from the PSD. Maximal enhancement of CaM-kinase II activity was observed when autophosphorylated or Ca(2+)/CaM-bound forms of the enzyme were proteolyzed. Analysis of the proteolytic products by Western blotting with a polyclonal antibody raised against soluble CaM-kinase II indicated that both proteases generated several immunoreactive fragments between 21 and 32 kDa. However, unlike chymotrypsin, mu-calpain degraded only a small fraction of the intact kinase subunits. (125)I-labeled CaM overlays indicated a major CaM-binding fragment of approximately 23 kDa in mu-calpain digests of purified cytosolic CaM-kinase II. This fragment was also shown to contain the regulatory autophosphorylation site (Thr-286(alpha)/287(beta)) of the kinase. Immunoblotting with antibody to the catalytic domain of the kinase indicated that there was a single active fragment of approximately 30 kDa in the mu-calpain digests. Analysis of the crude digests on a Superose-6 FPLC column also indicated that the Ca(2+)/CaM-independent activity resided in a fragment of approximately 30 kDa. This catalytic fragment did not bind to CaM-Sepharose. Thus, mu-calpain appears to cleave CaM-kinase 11 into a 30-kDa catalytic domain fragment and a 23-kDa regulatory domain fragment. A putative mechanism for persistent regulation of synaptic events by such a proteolytic activation of CaM-kinase 11 is discussed.
 ...
PMID:Proteolytic activation of calcium/calmodulin-dependent protein kinase II: Putative function in synaptic plasticity. 1991 59

The largest component of the human heart, the left ventricle (LV), plays a major role in delivering blood throughout the body. Therefore, an in-depth detailed quantitative proteome analysis of the human LV is a valuable resource. For this purpose, a multifaceted proteomics approach combining differential sample fractionations (gel, strong cation exchange (SCX)), enzymatic digestions (trypsin, chymotrypsin, LysN), and peptide fragmentation techniques (CID and ETcaD) was used to enhance protein sequence coverage, identification confidence and quantitative abundance determination. Using stringent criteria, 3584 distinct proteins could be identified from the latest well-annotated Swissprot database (23,000 entries). Commutatively, the over 130,000 identified MS/MS spectra were used to assess concentrations of each identified LV protein through a combination of spectral counting methods. Among the most concentrated proteins, many currently used biomarkers for detection of myocardial infarction reside. These cardiac leakage markers have a good diagnostic power, but their prognostic potential seems limited. Discovery of markers that represent etiological determinants of cardiac disease require a shift of focus towards the signaling proteome. Therefore, a protein-class centered quantitative analysis of kinases, phosphatases and GTPases was adopted. These comparative analyses revealed many cardiac involved kinases (PKA, CaMKII, ERK) to reside among the most abundant signaling proteins, and also to mediate many observed in vivo phosphorylation sites. The abundance chart of signaling proteins may assist in identifying novel functional pathways, for instance through the abundant, but relatively little known, kinases STK38L and OXSR1. The obtained quantitative protein library of the human left ventricle is a valuable resource to isolate signaling based, putative biomarkers with concentrations likely to be detectable in plasma.
 ...
PMID:Proteome-wide protein concentrations in the human heart. 2059 66

Synapsins are synaptic vesicle-associated phosphoproteins that play a major role in the fine regulation of neurotransmitter release. In Drosophila, synapsins are required for complex behavior including learning and memory. Synapsin isoforms were immunoprecipitated from homogenates of wild-type Drosophila heads using monoclonal antibody 3C11. Synapsin null mutants (Syn(97)) served as negative controls. The eluted proteins were separated by SDS-PAGE and visualized by silver staining. Gel pieces picked from five bands specific for wild type were analyzed by nano-LC-ESI-MS/MS following multienzyme digestion (trypsin, chymotrypsin, AspN, subtilisin, pepsin, and proteinase K). The protein was unambiguously identified with high sequence coverage (90.83%). A number of sequence conflicts were observed and the N-terminal amino acid was identified as methionine rather than leucine expected from the cDNA sequence. Several peptides from the larger isoform demonstrated that the in-frame UAG stop codon at position 582 which separates two large open reading frames is read through by tRNAs for lysine. Seven novel phosphorylation sites in Drosophila synapsin were identified at Thr-86, Ser-87, Ser-464, Thr-466, Ser-538, Ser-961, and Tyr-982 and verified by phosphatase treatment. No phosphorylation was observed at the conserved PKA/CaM kinase-I/IV site (RRFS, edited to RGFS) in domain A or a potential PKA site near domain E.
 ...
PMID:Mass spectrometric analysis of synapsins in Drosophila melanogaster and identification of novel phosphorylation sites. 2102 12