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)

The specificity and mode of action of an acid proteinase (EC 3.4.23.6) from Aspergillus saitoi were investigated with oxidized B-chain of insulin, angiotensin II and bradykinin. Further purification of acid proteinase was performed with N,O-dibenzyloxycarbonyl-tyrosine hexamethylene-diamino-Sepharose 4B affinity chromatography and isoelectric focusing. The purified enzyme was free of any other proteolytic activity demonstrated in Asp. saitoi. Acid proteinase from Asp. saitoi hydrolyzed primarily two peptide bonds in the oxidized B-chain of insulin, the Leu(15)-Tyr(16) bond and the Phe(24)-Phe(25) bond. Additional cleavages of the bonds His(10)-Leu(11), Ala(14)-Leu(15) and Tyr(16)-Leu(17) were also noted. Primary splitting sites at Leu(15)-Tyr(16) and Phe(24-)-Phe(25) with acid proteinase from Asp. saitoi were identical with those reported in the work of cathepsin D (EC 3.4.23.5) from human erythrocyte. Hydrolysis of angiotensin II was observed at the Tyr(4)-Ile(5) bond. In conclusion, peptide bonds which have a hydrophobic amino acid such as phenylalanine, tyrosine, leucine and isoleucine in the P'1 position (as defined by Berger and Schechter, [29]) are preferentially cleaved by the trypsinogenactivating acid proteinase from Asp. saitoi.
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PMID:Purification of an acid proteinase from Aspergillus saitoi and determination of peptide bond specificity. 2 99

Leucine, but not isoleucine or valine, inhibited protein degradation and accelerated protein synthesis in hearts perfused with buffer that contained glucose (15 mM) and normal plasma levels of other amino acids, except for the branched chain compounds. Products of leucine, isoleucine, and valine metabolism also inhibited protein degradation and stimulated protein synthesis. These compounds included the transamination and decarboxylation products, as well as acetate, acetoacetate, and propionate. In some, but not all instances, inhibition of degradation and acceleration of synthesis were accompanied by an increase in intracellular leucine. When insulin was added to the perfusate, the rate of degradation was reduced by 40%, but addition of leucine was ineffective in the presence of the hormone. Insulin, leucine (2 mM) and a mixture of branched chain amino acids at normal plasma levels increased latency of cathepsin D in hearts that were perfused with buffer containing glucose. A combination of leucine and insulin increased latency more than either substance alone. These studies indicate that leucine as well as a variety of substrates that are oxidized in the citric acid cycle are involved in regulation of protein turnover in heart muscle.
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PMID:Effect of leucine and metabolites of branched chain amino acids on protein turnover in heart. 46 30

Peptides derived from enzymatic digestions (cathepsin D and trypsin) were characterized and amino acid sequences determined by using their LC/MS spectra. A Frit-FAB interface that produces extensive peptide fragmentation and permits amino acid sequencing at the low picomole level is described for a model antigen, Staphylococcus aureus nuclease (Nase), and an enzyme of unknown structure, yeast aminopeptidase B. The amino acid sequences of peptides derived from digestion of Nase with cathepsin D (a relatively nonspecific endoprotease) were readily deduced and have provided insights into the nature of antigen processing. Frit-FAB LC/MS spectra of the Nase peptides contained a sufficient number of fragment ions to conclusively identify peptides with a mass below 2000 Da. Capillary LC/MS provided a means for the separation and identification of these enzymatically derived peptides in a fraction of the time that would have been required by gas-phase Edman sequence analysis. The optimized Frit-FAB experiment was consequently evaluated for the partial characterization of aminopeptidase B recently purified to homogeneity from Saccharomyces cerevisiae. Sequence-specific ions observed in the Frit-FAB mass spectra of these tryptic peptides were identical with those commonly observed in high-energy collision-induced dissociation (CID) spectra and included side-chain fragment ions that differentiated leucine from isoleucine. These fragment ions were used to deduce entire amino acid sequences for several of the tryptic peptides.
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PMID:Optimization of the fragmentation in a frit-fast atom bombardment ion source for the sequencing of peptides at the picomole level. 175 Jun 99

The acid proteases, pepsin, rennin and cathepsin D, were shown to generate mast cell histamine releasing peptides (HRP) when incubated with the albumin fraction of mammalian plasmas. Significant histamine release was observed using less than 1 microliter equivalent of pepsin-treated plasma. Histamine release was rapid, dependent on calcium and energy, and accompanied by degranulation. The major HRP present in pepsin-treated human and canine plasma was identified as H-Ile-Ala-Arg-Arg-His-Pro-Tyr-Phe-OH whereas that from rat plasma had valine substituted for isoleucine. Cathepsin D-treated BSA gave rise to the human octapeptide (above) as well as to an extended decapeptide with H-Tyr-Glu- at the N-terminus. These peptides were apparently derived from one region of serum albumin, residues 139 to 149 of the human, canine, or bovine sequence. We hypothesize that cathepsin D, released from leukocyte lysosomes, might generate HRP during the delayed phase of an inflammatory response.
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PMID:Structures of histamine-releasing peptides formed by the action of acid proteases on mammalian albumin(s). 247 9

Plasmodium requires a living cell for growth and reproduction. Intraerythrocytically the parasite stores no reserve carbohydrate, relying entirely on host-supplied glucose and certain amino acids (glutamic acid) for its energy. Plasmodia are microaerophiles degrading glucose primarily to lactate rather than to CO2. The limited amounts of oxygen utilized may serve for biosynthetic purposes (e.g. pyrimidine biosynthesis) rather than being involved in an energy-yielding electron transport chain. Evidence for a parasite pentose pathway is weak since glucose-6-phosphate dehydrogenase has rarely been found; paradoxically, activity for 6-phosphogluconate dehydrogenase, the next enzyme in the pathway, is consistently identified. The parasites synthesize pyrimidines de novo, but being incapable of de novo purine biosynthesis they require preformed purines. Exogenously supplied purine, notably hypoxanthine derived from catabolism of erythrocytic ATP, is taken up and incorporated whereas pyrimidines are not. The capacity for de novo amino acid biosynthesis is limited and presumably haemoglobin supplies most of the amino acids required by the parasite. Degradation of haemoglobin, involving parasite proteases, notably a cathepsin D-like enzyme, leaves a characteristic golden-brown residue, haemozoin. Haemozoin consists of dimers of ferriprotoporphyrin IX, methaemoglobin and plasmodial proteins. For some species, isoleucine and methionine must be supplied exogenously for good plasmodial growth. Infected erythrocytes characteristically show altered permeability properties, changes which in large part contribute to parasite growth while at the same time impairing red cell function.
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PMID:Metabolism and surface transport of parasitized erythrocytes in malaria. 655 Dec 36

Cathepsin D is a lysosomal aspartic proteinase that has been implicated in several pathological processes such as breast cancer and Alzheimer's disease. We designed and synthesized a number of quenched fluorogenic substrates with P2 variations in the series AcEE(EDANS)KPIXFFRLGK(DABCYL)E-NH2, where X=cysteine, methylcysteine, ethylcysteine, tert-butylcysteine, carboxymethylcysteine, methionine, valine or isoleucine. Most of the fluorogenic substrates exhibited greater k(cat)/Km ratios than the best cathepsin D substrates described so far. Differences in kinetic constants, which were rationalized using structure-based modeling, might make certain substrates useful for particular applications, such as active site titrations or initial velocity determination using a fluorescent plate reader.
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PMID:Design of sensitive fluorogenic substrates for human cathepsin D. 928 Mar 16

Cathepsin E and cathepsin D are two major intracellular aspartic proteinases implicated in the physiological and pathological degradation of intra- and extracellular proteins. In this study, we designed and constructed highly sensitive synthetic decapeptide substrates for assays of cathepsins E and D based on the known sequence specificities of their cleavage sites. These substrates contain a highly fluorescent (7-methoxycoumarin-4-yl)acetyl (MOCAc) moiety and a quenching 2,4-dinitrophenyl (Dnp) group. When the Phe-Phe bond is cleaved, the fluorescence at an excitation wavelength of 328 nm and emission wavelength of 393 increases due to diminished quenching resulting from the separation of the fluorescent and quenching moieties. The first substrate, MOCAc-Gly-Lys-Pro-Ile-Leu-Phe-Phe-Arg-Le u-Lys(Dnp)gamma-NH2, in which the Lys-Pro combination at positions P5 and P4 was designed for specific interaction with cathepsin E, is hydrolyzed equally well by cathepsins E and D (kcat/Km = 10.9 microM(-1) x s(-1) for cathepsin E and 15.6 microM(-1) x s(-1) for cathepsin D). A very acidic pH optimum o was obtained for both enzymes. The second substrate, MOCAc-Gly-Lys-Pro-Ile-Ile-Phe-Phe-Arg-Le u-Lys(Dnp)gamma-NH2, in which the isoleucine residue at position P2 was meant to increase the specificity for cathepsin E, is also hydrolyzed equally by both enzymes (kcat/Km = 12.2 microM(-1) x s(-1) for cathepsin E and 16.3 microM(-1) x s(-1) for cathepsin D). The kcat/Km values for both substrates are greater than those for the best substrates for cathepsins E and D described so far. Unfortunately, each substrate shows little discrimination between cathepsin E and cathepsin D, suggesting that amino acids at positions far from the cleavage site are important for discrimination between the two enzymes. However, in combination with aspartic proteinase inhibitors, such as pepstatin A and Ascaris pepsin inhibitor, these substrates enable a rapid and sensitive determination of the precise levels of cathepsins E and D in crude cell extracts of various tissues and cells. Thus these substrates represent a potentially valuable tool for routine assays and for mechanistic studies on cathepsins E and D.
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PMID:Characterization of new fluorogenic substrates for the rapid and sensitive assay of cathepsin E and cathepsin D. 1034 17

We obtained DNA, brains, and eyes from American Bulldogs with neurodegeneration due to neuronal ceroid lipofuscinosis (NCL). The diagnosis of NCL was confirmed by detection of autofluorescent cytoplasmic inclusions within neurons throughout the brains, in retinal ganglion cells, and along outer limiting membranes of the retinas. Electron microscopy revealed that the inclusions had coarsely granular matrices surrounding well-delineated spherical structures and that the inclusions near the retinal outer limiting membranes were within photoreceptor cells, mostly cones. Affected American Bulldogs were homozygous for the A allele of a G to A transition in the cathepsin D gene (CTSD), which predicts the conversion of methionine-199 to an isoleucine. Only the G allele was detected in DNA samples from 131 randomly selected dogs representing 108 breeds other than American Bulldog; however, the A allele had a frequency of 0.28 among 123 genotyped American Bulldogs. Transmission analysis in a 99 dog pedigree of American Bulldogs indicated a probability of less than 10(-7) that alleles from any mutation unlinked to CTSD would be concordant with the pedigree and phenotypes of the dogs. Brain samples from affected dogs had 36% of the cathepsin D-specific enzymatic activity found in control dog brains; whereas, specific enzymatic activities of 15 other lysosomal enzymes were unchanged or increased. Compared to previously described NCLs in mice and sheep that completely lack cathepsin D activity, the clinical course of NCL in the American Bulldogs was less severe and more closely resembled that of many human NCLs.
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PMID:A mutation in the cathepsin D gene (CTSD) in American Bulldogs with neuronal ceroid lipofuscinosis. 1638 34