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An enzyme that acts upon the centrally located peptide bonds of a protein molecule.



an enzyme of the class of hydrolases. Endo-peptidases catalyze the decomposition of internal peptide bonds in proteins and peptides. The speed of hydrolysis of a given peptide bond by different endopeptidases depends on the substrate specificity of the enzyme and the spatial accessibility of the given peptide bond, especially if the substrate is a native, not denatured, protein. It does not depend on the size of the molecules of the substrate, that is, the length of the polypeptide chain. The substrate specificity of an endopeptidase consists in the ability of a given enzyme to hydrolyze the peptide bonds between certain amino acid residues with the greatest speed. For example, chy-motrypsin very rapidly hydrolyzes peptide bonds together with aromatic amino acids; trypsin does the same with diamino acids. Endopeptidases are classified as extracellular or intracellular (tissular). Extracellular endopeptidases are secreted into the digestive cavity of animals (for example, enterokinase) or simply into the external environment (the exo-enzymes of bacteria).

The use of endopeptidases in determining the primary structure of proteins is based on their properties.

References in periodicals archive ?
Abbreviations: CNBr, cyanogen bromide; Lys-C, endoproteinase Lys-C; MS, mass spectrometry; OCC, oral cavity cancer; RPLC-MS, reverse phase liquid chromatography-mass spectrometry; SCX, strong cation exchange chromatography.
Enzymatic digests of native lectin protein with endoproteinase C were separated by RP-HPLC and subjected to protein sequencing, resulting in the partial N-terminal and an internal fragment of amino acid sequence of lectin, identified to be sequence PLQGRSQKTE and GNEDCLDLRT, respectively.
Because antibody 15 and 16 are specifically directed against N-terminal domain, the immunoprecipitation of ~21-kDa fragments from endoproteinase Asp-N treated [sup.
Treatment of foliar chips for 48 h with the proteolytic enzymes (carboxypeptidase B, endoproteinase glu-C, and subtilisin) also led to the partial removal of the foliar globules.
To obtain the COOH-terminal sequence, samples were digested with sequencing grade endoproteinase Glu-C (Endo Glu-C; Boehringer-Mannheim), and the resulting fragments were purified by RP-HPLC with TFA as counterion.
Partially deglycosylated immunoaffinity-purified samples were digested with trypsin or endoproteinase Glu-C or by a combination of both enzymes in 50 mmol/L ammonium bicarbonate containing 1 mmol/L calcium dichloride, pH 8.
1c] measurement, which involved the proteolysis of hemoglobins using endoproteinase Glu-C and hydrolysis of hexapeptide calibration standards using HCl.
In accordance with the IFCC protocol, peptide linkages C-terminal to the glutamic acid residues in Hb components in the hemolysates were cleaved with endoproteinase Glu-C (Sigma-Aldrich) (1).
In contrast, a digestion with endoproteinase Asp-N, taking advantage of the higher abundance of aspartic acids in pepsinogen, yields a number of potential target peptides for an SRM assay.
Such a system has been developed consisting of incubation with the enzyme endoproteinase Glu-C, cleavage of the N-terminal hexapeptide of the [beta] chain, and separation and quantification of glycated and non-glycated hexapeptides by mass spectrometry or capillary electrophoresis (3).
1c] is based on the ratio of glycated to nonglycated N-terminal hexapeptides of the [beta]-chains of hemoglobin after digestion with Glu-C endoproteinase.
Three separate enzymatic digestion protocols were used: digestion with trypsin, with endoproteinase Glu-C, and with endoproteinase Glu-C, followed by digestion with endoproteinase Lys-C.