Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.31.1 (micrococcal nuclease)
 2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism by which changes in diet mediate levels of exportable enzymes and proenzymes in pancreatic tissue were studied in rats. The relative levels of mRNA coding for pancreatic amylase, lipase, procarboxypeptidases A and B, and the family of serine protease zymogens have been determined by the ability of isolated RNA to direct the synthesis of these products in a high-fidelity micrococcal nuclease-treated reticulocyte-lysate translation system. Translation products synthesized in vitro correlated directly with products synthesized in vivo in pancreatic lobules. Dietary adaptation was observed when dietary carbohydrate was increased from 0 to 58% at the expense of protein (81-23%). The increase in dietary carbohydrate over this range resulted in a 2-fold increase in amylase synthesis in pancreatic lobules and a 1.8-fold increase in mRNA-directed synthesis of amylase in the translation system in vitro. Concomitant with the decrease in dietary protein, synthesis of serine protease zymogens in pancreatic lobules and in the system in vitro decreased by approximately 50%. Over this range of dietary manipulation, ratios of amylase to serine proteases showed a 3.6-fold change. When dietary carbohydrate was further increased to 81% and protein reduced to 0, non-adaptive changes were observed since there was a decrease in amylase synthesis under conditions both in vivo and in vitro. mRNAs coding for pancreatic lipase and procarboxypeptidases A and B were unaffected by the dietary changes. These findings indicate that nutritional regulation in the tissue levels of pancreatic enzymes and proenzymes is mediated by changes in the content of active cytoplasmic mRNAs.
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PMID:Dietary regulation of levels of active mRNA coding for amylase and serine protease zymogens in the rat pancreas. 619 2

A secretion reporter system based on Staphylococcus aureus nuclease (nuc) was developed for use in mycobacteria. Fusion of secretion signals to the reporter cloned in a shuttle vector, pBPnuc1, resulted in halo formation around colonies of Mycobacterium smegmatis and Mycobacterium tuberculosis grown on DNase agar plates containing Methyl Green indicator dye. This in-situ detection system was used to identify secreted proteins by screening a pBPnuc1::H37Rv nuc gene fusion library in M. smegmatis. The clones identified in this screen all formed colony halos when present in M. tuberculosis grown on indicator media. The proteins corresponded to DesA2, a stearoyl-acyl carrier protein desaturase, PepA, a putative serine protease and the Apa antigen, which is the ATP-binding subunit of an ABC transport system. Of these proteins, only PepA and Apa contained recognizable leader peptides.
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PMID:Staphylococcus aureus nuclease is a useful secretion reporter for mycobacteria. 1054 30

Understanding the regulation of physiological processes requires detailed knowledge of the recognition of substrates by enzymes. One of the most productive model systems for the study of enzyme-substrate interactions is the serine protease family; however, most studies of protease action have used small substrates that contain an activated, non-natural scissile bond. Because few kinetic or structural studies have used protein substrates, the physiologically relevant target of most proteases, it seems likely that important mechanisms of substrate recognition and processing by proteases have not yet been fully elucidated. Consistent with this hypothesis, we have observed that K(m) values for protein substrates are reduced as much as 200-15000-fold relative to those of analogous peptide substrates. Here we examine the thermodynamic consequences of interactions between proteases and their substrates using staphylococcal nuclease (SNase) and SNase variants as model protein substrates. We have obtained values for enthalpy, entropy, and K(d) for binding of proteins and peptides by the nonspecific protease trypsin and the highly specific protease urokinase-type plasminogen activator (u-PA). To avoid cleavage of substrates during these measurements, we used inactive variants of trypsin and u-PA whose catalytic serine S195 had been replaced by alanine. Differences in the K(d) values for binding of protein and peptide substrates closely approximate the large differences observed in the corresponding K(m) values. Improved binding of protein substrates is due to decreased enthalpy, and this effect is pronounced for the selective protease u-PA. Fundamental differences in recognition of analogous protein and peptide substrates may have influenced the evolution of protease specificity.
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PMID:Binding of nonphysiological protein and peptide substrates to proteases: differences between urokinase-type plasminogen activator and trypsin and contributions to the evolution of regulated proteolysis. 1273 81