Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.23.5 (cathepsin D)
4,130 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Myelin basic protein (MBP) extracted from human delipidated white matter was found to be degraded at pH 3.0 by endogenous proteolytic activities of extracts. Electrophoretic peptide patterns were consistent with limited proteolysis of MBP. Based on pH, activation by EDTA and DTE, and inhibition by p-CMPS, E-64 and, in particular, by leupeptin, the protease involved was tentatively identified as cathepsin B or a cathepsin B-like enzyme. As pepstatin failed to inhibit acid proteolysis of MBP cathepsin D was ruled out.
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PMID:Elucidation of cathepsin B-like activity associated with extracts of human myelin basic protein. 257 12

Brain cathepsin D, purified by affinity chromatography on Sepharose pepstatin columns, was incubated with synthetic peptides corresponding to the susceptible regions of the myelin basic protein encompassing the two Phe-Phe bonds. One peptide, Leu-Gly-Arg-Phe-Phe-Gly-Gly, was cleaved by cathepsin D at the Phe-Phe bond while another, Val-His-Phe-Phe-Lys-Asn-Gly, was resistant to cleavage. To determine if this was a result of His flanking the Phe-Phe bond, or chain length on the N-terminal side, two decapeptides were synthesized differing only in the presence or absence of His adjacent to Phe. The results show that both of the decapapetides were cleaved by cathepsin D at the Phe-Phe linkages. In addition, prolonged incubation led to release of N-terminal Lys, indicating an additional cleavage at the Phe-Lys bond. In contrast to the limited cleavage by cathepsin D, pepsin split all four peptides. These results support earlier work on the limited proteolysis of basic protein at the Phe-Phe bond and suggest additional sites upon prolonged exposure. Such peptides may have utility as alternative substrates for basic protein or as models for subsequent synthesis of possible inhibitors of the enzyme.
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PMID:Specificity of brain cathepsin D: cleavage of model peptides containing the susceptible Phe-Phe regions of myelin basic protein. 615 30

In aqueous solution bovine myelin basic protein has a close-to-random coil structure that is partially transformed to helix on interaction with lipids. Circular dichroism spectra have been used to follow this conformational transition which, with phospholipids, decreases in the order phosphatidylglycerol, phosphatidic acid approximately equal to phospholipids, decreases in the order phosphatidylethanolamine. There appears to be a strong correlation between the extent of alpha-helix formation and the degree of penetration of the hydrophobic region of the bilayer, as assessed by other methods. Cholesterol mixed in bilayers with phosphatidylserine has little effect on the protein secondary structure. Although basic protein binds strongly to cerebroside and to cerebroside sulphate, two of the other major myelin lipids, the intrinsic chirality of these lipids precludes assessment of their effect on the protein conformation. No significant changes in the circular dichroism spectra accompany the protein association with either of the zwitterionic bilayer-forming lipids, phosphatidylethanolamine and phosphatidylcholine. This seems to exclude extensive penetration into bilayers of these lipids and hence to exclude appreciable hydrophobic interactions; on the other hand, it is argued that little evidence exists for ionic attractions to these lipids. The optical activity of peptides derived from the basic protein by cleavage at the 42-43 and 88-89 peptides bonds (with cathepsin D) and at the 115-116 bond (with a skatole derivative) has also been measured in an attempt to locate the helix-forming regions within the primary structure.
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PMID:Dependence on lipid structure of the coil-to-helix transition of bovine myelin basic protein. 616 92

The degradation of bovine myelin basic protein by bovine brain cathepsin D (ED 3.4.23.5) was studied over a pH range of 2.75 - 6.0. Throughout this pH range pepstatin, an inhibitor of cathepsin D, prevented the degradation. The degradation at a pH away from the optimum of pH 3.5 was predictably slower, but also resulted in more restricted cleavage. Above pH 4.5 bovine basic protein peptide 1 - 42 was not degraded further to peptide 1 - 36 as occurs at pH 3.5. Additionally, at pH 5.5 another fragment of basic protein, peptide 1 - 91, persisted indicating that under certain basic protein as well as basic protein peptide 43 - 169 may be cleaved in the molecular region of basic protein around the phenylalanyl-phenylalanine residues at position 88 - 89. The small amount of peptides 1 - 91 and 92 - 169 detected at pH 5.5 suggests that the bond between residues 91 and 92 in intact basic protein is a minor cleavage site. The options and variation in cleavage around residues 88 - 92 of basic protein presumably result from pH-dependent changes in conformation in the is region but could also be due to changes in conformation of cathepsin D. These results indicate that local tissue changes such a pH amy affect not only the velocity of the reaction but also the nature of th product formed by the degradation of basic protein by brain cathepsin D
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PMID:The influence of pH on the degradation of bovine myelin basic protein by bovine brain cathepsin. 617 Mar 37

Studies were undertaken to determine of a previously unrecognized or inaccessible antigenic determinant might be exposed during the course of digestion of basic protein by a normal brain enzyme. As studied by double antibody radioimmunoassay, exposure of bovine brain myelin basic protein to bovine brain cathepsin D led to the appearance of an antigenic determinant recognized by an antibody reactive predominantly with the molecular region of BP encompassing residues 79-88. The 5 major microheterogeneous components of basic protein demonstrated this phenomenon. These results indicate that a normally appearing enzyme in brain known to the present in a number of cell types including oligodendrocytes can lead to the appearance of peptides of basic protein whose antigenic determinants may not be revealed in the intact molecule. This finding suggests that a number of basic protein peptides may be released by a similar mechanism so that efforts made to detect and quantitate such peptides must be capable of recognizing their unique antigenic features.
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PMID:The appearance of a new antigenic determinant during the degradation of myelin basic protein. 617 12

Free and membrane-bound polyribosomes were isolated from the forebrain of actively myelinating 24-day-old rats. The poly(A)+ RNA (polyadenylated RNA) extracted from both fractions was translated in vitro in reticulocyte lysates [Hall & Lim (1981) Biochem. J. 196. 327-336] in the presence or absence of a heterologous microsomal membrane fraction from dog pancreas. The rat myelin basic proteins synthesized in vitro were isolated by CM-cellulose chromatography and by immunoprecipitation with purified anti-(myelin basic protein) antibody. The large (mol.wt. 18 500) and small (mol.wt. 16 000) myelin basic proteins were translational products of poly(A)+ RNA from both free and membrane-bound polyribosomes. The identity of the myelin basic proteins was verified by analysis of peptides generated by the cathepsin D digestion of the immunoprecipitated proteins synthesized in vitro, in comparison with authentic rat myelin basic proteins. Although several other translational products of membrane-bound polyribosomal poly(A)+ RNA were modified when microsomal membranes were present during translation, molecular weights of the myelin basic proteins themselves were unchanged. The myelin basic proteins synthesized in vitro also did not differ significantly in size from the authentic myelin basic proteins, indicating that these membrane proteins are unlikely to be synthesized as substantially larger precursor molecules. The presence of the specific mRNA species on both free and membrane-bound polyribosomes is compatible with the extrinsic location of the myelin basic proteins on the cytoplasmic surface of the myelin membrane.
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PMID:The polyadenylated RNA directing the synthesis of the rat myelin basic proteins is present in both free and membrane-bound forebrain polyribosomes. 617 99

Myelin basic protein (MBP), an extrinsic membrane protein from the myelin sheath, binds dicyanohemin. The binding generates absorption bands in the Soret region and quenches the fluorescence emitted by the sole tryptophan residue. The absorption titration curves in the Soret demonstrate that the binding is stoichiometric, one heme per protein, with a large value of the extinction coefficient (8 X 10(4) M-1 cm-1 at 420 nm). Fluorescence quenching titration curves indicate an identical stoichiometry and a low quenching efficiency of 20%. From the heme titration curve the association constant between dicyanohemin and MBP is estimated to be greater than or equal to 10 nM-1 in 50 mM 4-morpholinepropanesulfonic acid buffer, pH 7.0, at 20 degrees C. Digestion of MBP by Staphylococcus aureus V8 protease yields a peptide (38-118) whose heme binding properties are identical to those of MBP. In contrast, peptides obtained by digestion of MBP with cathepsin D do not exhibit any specific binding of dicyanohemin. The cleavage of the Phe-Phe (42-43) bond appears to be critical in this respect. A comparison of the sequence immediately preceding, including these residues with a probable heme binding site of a mitochondrial cytochrome b, reveals a high degree of homology. The possible significance of heme binding is discussed.
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PMID:A heme binding site on myelin basic protein: characterization, location, and significance. 620 38

The possible mitogenic effects of a number of preparations of the myelin basic protein (MBP) of human brain have been investigated in various cell types in culture, including human amniotic fluid cells. Intact human MBP, as well as fragments derived by BNPS-skatole and cathepsin D treatment, and isoelectric focusing fractions of human MBP, showed no mitogenic activity. These results are consistent with recent findings that the fibroblast growth factor (FGF) activity of bovine brain does not originate from MBP.
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PMID:Fragments of myelin basic protein derived from human brain are not mitogenic in cultures of human amniotic fluid cells and other cells. 620 97

We have investigated the early steps of myelin basic protein (MBP) degradation in a membrane mimetic system (reverse micelles), resembling the interlamellar aqueous spaces where the protein is located in the myelin sheath. MBP, unfolded in buffer, refolds on incorporation into the micelles, resulting in reduced accessibility to three proteolytic enzymes, trypsin, cathepsin D, and Staphylococcus aureus V8 protease, in comparison with aqueous solution. Eleven cleavage sites seen in buffer are removed from proteolytic attack in micellar solution. These sites delineate a protected protein domain displaying a potential beta-sheet structure capable of interacting with the myelin membrane. An additional site not seen in buffer is attacked in the micelles. Experiments with a structure inducer, 15% 1-propanol in buffer, reveal that the refolding pattern of MBP in reverse micelles is specific to the membrane biomimetic system and is not produced by organic solvent per se. Micellar digestions of MBP generate long peptides, two of which, isolated after tryptic digestion, have been found to be immunodominant in multiple sclerosis patients. The findings suggest the structure induced in MBP by the micelles resembles that leading to production of the self-peptides recognized by T cells during proteolytic breakdown of MBP in autoimmune demyelinating diseases.
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PMID:Limited proteolysis of myelin basic protein in a system mimetic of the myelin interlamellar aqueous space. 768 Oct 99

Proteinase levels are increased in multiple sclerosis (MS) lesions and are implicated in demyelination. The cellular origins of the activity are not known, but inflammatory cells of hematogenous origin are one possibility. We studied the levels of two lysosomal proteinases implicated in the proteolysis of myelin basic protein, cathepsin B (CB) and cathepsin D (CD), in peripheral blood mononuclear cells (PBMCs) of 20 stable relapsing-remitting MS patients. We prepared and assayed cell lysates of PBMCs from the MS patients, 10 patients with other neurologic diseases (OND), and 12 normal controls (NC). Mean CB activity expressed as milliunits of activity per million cells was significantly increased in MS patients (7.86 +/- 0.54) compared with OND (6.80 +/- 0.74) and NC (5.94 +/- 0.28) cells (p < 0.05). CD levels were not significantly increased. To determine whether the increase was generalized or limited to a subset of cells, PBMCs were fractionated by plate adherence. CB levels in the adherent fraction (AD) of the 20 MS patients were higher than in the nonadherent fraction (NA), and the AD:NA ratio of CB in MS was higher than that in controls. This would be consistent with an increase in CB levels in monocytes and macrophages, cells known to be activated in the peripheral blood of MS patients and implicated as effectors of demyelination.
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PMID:Increased cathepsin B activity in peripheral blood mononuclear cells of multiple sclerosis patients. 816 36


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