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PubMed1990

The action of leucyl-leucine methyl ester on cytotoxic lymphocytes requires uptake by a novel dipeptide-specific facilitated transport system and dipeptidyl peptidase I-mediated conversion to membranolytic products.

The mechanism of toxicity for cytolytic lymphocytes of Leu-Leu-OMe and related dipeptide derivatives was examined. Selective inhibition of dipeptidyl peptidase I (DPPI), a lysosomal thiol protease highly enriched in cytotoxic lymphocytes, prevented all natural killer (NK) toxic effects of such agents. However, many DPPI substrates were found to possess no NK toxic properties. For some such agents, this lack of NK toxicity appeared to be related to the lack of uptake by lymphocytes. In this regard, Leu-Leu-OMe was found to be incorporated by lymphocytes and monocytes via a saturable facilitated transport mechanism with characteristics distinct from previously characterized mammalian dipeptide transport processes. This novel transport process was found to be specific for dipeptides composed of selective L-stereoisomer amino acids and enhanced by hydrophobic ester or amide additions to the COOH terminus of dipeptides. Maximal rates of Leu-Leu-OMe uptake by T8 and NK cell-enriched peripheral blood lymphocytes (PBL) were four- to sixfold higher than for T4-enriched PBL or PBL depleted of Leu-Leu-OMe-sensitive cytotoxic lymphocytes. All dipeptide amides or esters with NK toxic properties were found to act as competitive inhibitors of [3H]Leu-Leu-OMe uptake by PBL. However, some NK nontoxic DPPI substrates were found to be comparable with Leu-Leu-OMe in avidity for this transport process. Such agents were noted to possess one or more hydrophilic amino acid side chains and were found not to mediate red blood cell lysis when subjected to the acyl transferase activity of DPPI. Thus, uptake by a dipeptide-specific facilitated transport mechanism and conversion by DPPI to hydrophobic polymerization products with membranolytic properties were found to be common features of NK toxic dipeptide derivatives. The presence of a previously unreported dipeptide transport mechanism within blood leukocytes and the selective enrichment of the granule enzyme, DPPI, within cytotoxic effector cells of lymphoid or myeloid lineage appear to afford a unique mechanism for the targeting of immunotherapeutic reagents composed of simple dipeptide esters or amides.

Acyltransferases↗
PubMed1982

Dipeptidyl(amino)peptidase IV (DAP-IV) histochemistry on normal and pathologic lymphoid tissues.

The enzyme glycyl-proline-naphthylamidase (dipeptidyl-amino-peptidase IV), (DAP-IV) has been histochemically analysed in normal and pathological specimens of different lymphoid tissues. In all the tissues examined, the enzyme appeared to be highly specific for T cells. Using chloroformacetone fixation and sections of proper thickness, DAP-IV could be successfully demonstrated in cortical thymocytes, which exhibited weak reactivity, as well as in medullary thymocytes which showed a more intense and variable reactivity. A similar reactivity was observed in T cells of peripheral blood, lymph node, and spleen. Various acute lymphoblastic and nonlymphoblastic leukemias and malignant lymphomas were studied using the histochemical method for DAP-IV. Malignant cells from all the acute leukemias and from the B-cell lymphomas were DAP-IV unreactive, while strong reactivity was observed in one case of T-CLL and one case of T-PLL. The possible relationship of DAP-IV positivity pattern with T-cell maturation and its potential use as a diagnostic tool in lymphoproliferative disorders are discussed.

Bone Marrow↗
PubMed2001

Purification, molecular cloning, and immunohistochemical localization of dipeptidyl peptidase II from the rat kidney and its identity with quiescent cell proline dipeptidase.

We purified dipeptidyl peptidase II (DPP II) to homogeneity from rat kidney and determined its physicochemical properties, including its molecular weight, substrate specificity, and partial amino acid sequence. Furthermore, we screened a rat kidney cDNA library, isolated the DPP II cDNA and determined its structure. The cDNA was composed of 1,720 base pairs of nucleotides, and 500 amino acid residues were predicted from the coding region of cDNA. Human quiescent cell proline dipeptidase (QPP) cloned from T-cells is a 58-kDa glycoprotein existing as a homodimer formed with a leucine zipper motif. The levels of amino acid homology were 92.8% (rat DPP II vs. mouse QPP) and 78.9% (rat DPP II vs. human QPP), while those of nucleotide homology were 93.5% (rat DPP II vs. mouse QPP) and 79.4% (rat DPP II vs. human QPP). The predicted amino acid sequences of rat DPP II and human and mouse QPP possess eight cysteine residues and a leucine zipper motif at the same positions. The purified DPP II showed similar substrate specificity and optimal pH to those of QPP. Consequently, it was thought that DPP II is identical to QPP. Northern blot analysis with rat DPP II cDNA revealed prominent expression of DPP II mRNA in the kidney, and the order for expression was kidney >> testis > or = heart > brain > or = lung > spleen > skeletal muscle > or = liver. In parallel with Northern blot analysis, the DPP II antigen was detected by immunohistochemical staining in the cytosol of epithelial cells in the kidney, testis, uterus, and cerebrum.

Amino Acid Sequence↗
PubMed2005

Aminopeptidases and dipeptidyl-peptidases secreted by the dermatophyte Trichophyton rubrum.

The nature of secreted aminopeptidases in Trichophyton rubrum was investigated by using a reverse genetic approach. T. rubrum genomic and cDNA libraries were screened with Aspergillus spp. and Saccharomyces cerevisiae aminopeptidase genes as the probes. Two leucine aminopeptidases, ruLap1 and ruLap2, and two dipeptidyl-peptidases, ruDppIV and ruDppV, were characterized and compared to orthologues secreted by Aspergillus fumigatus using a recombinant protein from Pichia pastoris. RuLap1 is a 33 kDa nonglycosylated protein, while ruLap2 is a 58-65 kDa glycoprotein. The hydrolytic activity of ruLap1, ruLap2 and A. fumigatus orthologues showed various preferences for different aminoacyl-7-amido-4-methylcoumarin substrates, and various sensitivities to inhibitors and cations. ruDppIV and ruDppV showed similar activities to A. fumigatus orthologues. In addition to endopeptidases, the four aminopeptidases ruLap1, ruLap2, ruDppIV and ruDppV were produced by T. rubrum in a medium containing keratin as the sole nitrogen source. Synergism between endo- and exopeptidases is likely to be essential for dermatophyte virulence, since these fungi grow only in keratinized tissues.

Amino Acid Sequence↗
PubMed2005

Tripeptidyl peptidase II. An oligomeric protease complex from Arabidopsis.

The breakdown of most nuclear and cytoplasmic proteins involves their partial cleavage by the 26S proteasome followed by further disassembly to free amino acids by the combined action of endo- and exopeptidases. In animals, one important intermediate exopeptidase is tripeptidyl peptidase (TPP)II, which digests peptide products of the 26S proteasome and other endopeptidases into tripeptides. Here, we describe the purification and characterization of TPPII from Arabidopsis (Arabidopsis thaliana). Like its animal counterparts, Arabidopsis TPPII exists as a soluble, approximately 5- to 9-MD complex. Two related species of 153 and 142 kD are present in the purified preparations that are derived from a single TPP2 gene. Sequencing by Edman degradation of the intact polypeptides and mass spectrometry of proteolytic fragments demonstrated that the 142-kD form mainly differs from the 153-kD form by a truncation at the C-terminal end. This serine protease is a member of the subtilisin superfamily and is sensitive to the inhibitors alanine-alanine-phenylalanine-chloromethylketone and butabindide, which are diagnostic for the TPPII subfamily. The Arabidopsis TPP2 gene is widely expressed in many tissue types with related genes evident in other plant genomes. Whereas the 26S proteasome is essential, TPPII appears not as important for plant physiology. An Arabidopsis T-DNA mutant defective in TPP2 expression displays no phenotypic abnormalities and is not hypersensitive to either amino acid analogs or the 26S proteasome inhibitor MG132. As a consequence, plants likely contain other intermediate exopeptidases that assist in amino acid recycling.

Amino Acid Sequence↗
PubMed1986

Dipeptidyl peptidases in bovine reproductive organs and secretions.

Dipeptidyl peptidases (DPP) I-IV were analysed in homogenates of bovine reproductive organs as well as in seminal vesicle secretions and seminal plasma. The presence of various molecular forms of these enzymes was studied by fractionation using gel filtration, anion exchange chromatography and chromatofocusing. The eluting enzymes were pooled, and their biochemical properties were briefly characterized. The histochemical localization of DPP II and IV was carried out with the most active tissues. DPP I and III were absent from seminal plasma, but their highest activity was found in the epididymis and increased during sexual maturation. DPP II was found mainly in a single molecular form and displayed a wide distribution in the reproductive organs. Its activity in seminal plasma may be derived from various organs, although the major sources are probably the apical activity in the epididymis, ampulla and seminal vesicle. DPP IV activity was high in the cauda epididymis, and ampulla, and in the seminal vesicles and their secretions. The high activity of DPP IV in seminal plasma appeared to derive from these organs, which showed a strong apical reaction of the epithelial lining. In seminal vesicles the enzyme was mainly secreted attached to membrane particles called vesiculosomes.

Animals↗
PubMed1992

Cathepsin B/L-, elastase-, tryptase-, trypsin- and dipeptidyl peptidase IV-like activities in gingival crevicular fluid: correlation with clinical parameters in untreated chronic periodontitis patients.

20 untreated chronic periodontitis patients were given a full periodontal examination, including measurements of probing depth (PD), clinical attachment loss (CAL), gingival index (GI), bleeding index (BI) and plaque index (Pl.I.). At a second visit, gingival crevicular fluid (GCF) was collected on filter paper strips from the deepest accessible probing site of each tooth. GCF volumes were determined and the samples eluted into buffer. Protease activities in the resulting eluates were assayed with peptidyl derivatives of 7-amino-4-trifluoromethyl coumarin (AFC). Cathepsin B/L-like activity was determined with Bz-Val-Lys-Lys-Arg-AFC, elastase-like activity with MeOSuc-Ala-Ala-Pro-Val-AFC, tryptase-like activity with Z-Ala-Ala-Lys-AFC, trypsin-like activity with Z-Gly-Gly-Arg-AFC and dipeptidyl peptidase (DPP) IV-like activity with Ala-Pro-AFC. Total enzyme activities and enzyme concentrations both correlated positively with all clinical parameters in linear regression analysis. This was true on both a patient level, using mean patient values, and a site level, using either individual patient or pooled patient data. Most of these correlations were statistically significant, although the proportion was greater for total enzyme activity than concentration. With total activities, correlations with different enzymes and parameters generally followed the order: cathepsin B/L-greater than elastase- greater than DPP IV- greater than trypsin- greater than tryptase-like activity and PD greater than CAL greater than GI greater than BI greater than Pl.I respectively. Total enzyme activities had good diagnostic specificity and sensitivity as predictors of clinical parameters in this cross-sectional study, suggesting that GCF proteases might provide useful information on the periodontal condition.

Adult↗
PubMed2006

Identification and characterization of two dipeptidyl-peptidase III isoforms in Drosophila melanogaster.

Dipeptidyl-peptidase III (DPP III) hydrolyses small peptides with a broad substrate specificity. It is thought to be involved in a major degradation pathway of the insect neuropeptide proctolin. We report the purification and characterization of a soluble DPP III from 40 g Drosophila melanogaster. Western blot analysis with anti-(DPP III) serum revealed the purification of two proteins of molecular mass 89 and 82 kDa. MS/MS analysis of these proteins resulted in the sequencing of 45 and 41 peptide fragments, respectively, confirming approximately 60% of both annotated D. melanogaster DPP III isoforms (CG7415-PC and CG7415-PB) predicted at 89 and 82 kDa. Sequencing also revealed the specific catalytic domain HELLGH in both isoforms, indicating that they are both effective in degrading small peptides. In addition, with a probe specific for D. melanogaster DPP III, northern blot analysis of fruit fly total RNA showed two transcripts at approximately 2.6 and 2.3 kb, consistent with the translation of 89-kDa and 82-kDa DPP III proteins. Moreover, the purified enzyme hydrolyzed the insect neuropeptide proctolin (Km approximately 4 microm) at the second N-terminal peptide bound, and was inhibited by the specific DPP III inhibitor tynorphin. Finally, anti-(DPP III) immunoreactivity was observed in the central nervous system of D. melanogaster larva, supporting a functional role for DPP III in proctolin degradation. This study shows that DPP III is in actuality synthesized in D. melanogaster as 89-kDa and 82-kDa isoforms, representing two native proteins translated from two alternative mRNA transcripts.

Animals↗
PubMed2007

Disposition of the dipeptidyl peptidase 4 inhibitor sitagliptin in rats and dogs.

The pharmacokinetics, metabolism, and excretion of sitagliptin [MK-0431; (2R)-4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine], a potent dipeptidyl peptidase 4 inhibitor, were evaluated in male Sprague-Dawley rats and beagle dogs. The plasma clearance and volume of distribution of sitagliptin were higher in rats (40-48 ml/min/kg, 7-9 l/kg) than in dogs ( approximately 9 ml/min/kg, approximately 3 l/kg), and its half-life was shorter in rats, approximately 2 h compared with approximately 4 h in dogs. Sitagliptin was absorbed rapidly after oral administration of a solution of the phosphate salt. The absolute oral bioavailability was high, and the pharmacokinetics were fairly dose-proportional. After administration of [(14)C]sitagliptin, parent drug was the major radioactive component in rat and dog plasma, urine, bile, and feces. Sitagliptin was eliminated primarily by renal excretion of parent drug; biliary excretion was an important pathway in rats, whereas metabolism was minimal in both species in vitro and in vivo. Approximately 10 to 16% of the radiolabeled dose was recovered in the rat and dog excreta as phase I and II metabolites, which were formed by N-sulfation, N-carbamoyl glucuronidation, hydroxylation of the triazolopiperazine ring, and oxidative desaturation of the piperazine ring followed by cyclization via the primary amine. The renal clearance of unbound drug in rats, 32 to 39 ml/min/kg, far exceeded the glomerular filtration rate, indicative of active renal elimination of parent drug.

Adenosine Deaminase↗
PubMed2007

Metabolism and excretion of the dipeptidyl peptidase 4 inhibitor [14C]sitagliptin in humans.

The metabolism and excretion of [(14)C]sitagliptin, an orally active, potent and selective dipeptidyl peptidase 4 inhibitor, were investigated in humans after a single oral dose of 83 mg/193 muCi. Urine, feces, and plasma were collected at regular intervals for up to 7 days. The primary route of excretion of radioactivity was via the kidneys, with a mean value of 87% of the administered dose recovered in urine. Mean fecal excretion was 13% of the administered dose. Parent drug was the major radioactive component in plasma, urine, and feces, with only 16% of the dose excreted as metabolites (13% in urine and 3% in feces), indicating that sitagliptin was eliminated primarily by renal excretion. Approximately 74% of plasma AUC of total radioactivity was accounted for by parent drug. Six metabolites were detected at trace levels, each representing <1 to 7% of the radioactivity in plasma. These metabolites were the N-sulfate and N-carbamoyl glucuronic acid conjugates of parent drug, a mixture of hydroxylated derivatives, an ether glucuronide of a hydroxylated metabolite, and two metabolites formed by oxidative desaturation of the piperazine ring followed by cyclization. These metabolites were detected also in urine, at low levels. Metabolite profiles in feces were similar to those in urine and plasma, except that the glucuronides were not detected in feces. CYP3A4 was the major cytochrome P450 isozyme responsible for the limited oxidative metabolism of sitagliptin, with some minor contribution from CYP2C8.

Adenosine Deaminase↗
PubMed2001

Purification and characterization of an X-prolyl-dipeptidyl peptidase from Lactobacillus sakei.

An X-prolyl-dipeptidyl peptidase has been purified from Lactobacillus sakei by ammonium sulfate fractionation and five chromatographic steps, which included hydrophobic interaction, anion-exchange chromatography, and gel filtration chromatography. This procedure resulted in a recovery yield of 7% and an increase in specificity of 737-fold. The enzyme appeared to be a dimer with a subunit molecular mass of approximately 88 kDa. Optimal activity was shown at pH 7.5 and 55 degrees C. The enzyme was inhibited by serine proteinase inhibitors and several divalent cations (Cu(2+), Hg(2+), and Zn(2+)). The enzyme almost exclusively hydrolyzed X-Pro from the N terminus of each peptide as well as fluorescent and colorimetric substrates; it also hydrolyzed X-Ala at the N terminus, albeit at lower rates. K(m) s for Gly-Pro- and Lys-Ala-7-amido-4-methylcoumarin were 29 and 88 microM, respectively; those for Gly-Pro- and Ala-Pro-p-nitroanilide were 192 and 50 microM, respectively. Among peptides, beta-casomorphin 1-3 was hydrolyzed at the highest rates, while the relative hydrolysis of the other tested peptides was only 1 to 12%. The potential role of the purified enzyme in the proteolytic pathway by catalyzing the hydrolysis of peptide bonds involving proline is discussed.

Animals↗
PubMed2006

Sedolisins, a new class of secreted proteases from Aspergillus fumigatus with endoprotease or tripeptidyl-peptidase activity at acidic pHs.

The secreted proteolytic activity of Aspergillus fumigatus is of potential importance as a virulence factor and in the industrial hydrolysis of protein sources. The A. fumigatus genome contains sequences that could encode a five-member gene family that produces proteases in the sedolisin family (MEROPS S53). Four putative secreted sedolisins with a predicted 17- to 20-amino-acid signal sequence were identified and termed SedA to SedD. SedA produced heterologously in Pichia pastoris was an acidic endoprotease. Heterologously produced SedB, SedC, and SedD were tripeptidyl-peptidases (TPP) with a common specificity for tripeptide-p-nitroanilide substrates at acidic pHs. Purified SedB hydrolyzed the peptide Ala-Pro-Gly-Asp-Arg-Ile-Tyr-Val-His-Pro-Phe to Arg-Pro-Gly, Asp-Arg-Ile, and Tyr-Val-His-Pro-Phe, thereby confirming TPP activity of the enzyme. SedB, SedC, and SedD were detected by Western blotting in culture supernatants of A. fumigatus grown in a medium containing hemoglobin as the sole nitrogen source. A degradation product of SedA also was observed. A search for genes encoding sedolisin homologues in other fungal genomes indicates that sedolisin gene families are widespread among filamentous ascomycetes.

Aminopeptidases↗
PubMed2000

Tripeptidyl peptidase II promotes maturation of caspase-1 in Shigella flexneri-induced macrophage apoptosis.

The invasive enteropathogenic bacterium Shigella flexneri activates apoptosis in macrophages. Shigella-induced apoptosis requires caspase-1. We demonstrate here that tripeptidyl peptidase II (TPPII), a cytoplasmic, high-molecular-weight protease, participates in the apoptotic pathway triggered by Shigella. The TPPII inhibitor Ala-Ala-Phe-chloromethylketone (AAF-cmk) and clasto-lactacystin beta-lactone (lactacystin), an inhibitor of both TPPII and the proteasome, protected macrophages from Shigella-induced apoptosis. AAF-cmk was more potent than lactacystin and irreversibly blocked Shigella-induced apoptosis by 95% at a concentration of 1 microM. Conversely, peptide aldehyde and peptide vinylsulfone proteasome inhibitors had little effect on Shigella-mediated cytotoxicity. Both AAF-cmk and lactacystin prevented the maturation of pro-caspase-1 and its substrate pro-interleukin 1beta in Shigella-infected macrophages, indicating that TPPII is upstream of caspase-1. Neither of these compounds directly inhibited caspase-1. AAF-cmk and lactacystin did not impair macrophage phagocytosis or the ability of Shigella to escape the macrophage phagosome. TPPII was also found to be involved in apoptosis induced by ATP and the protein kinase inhibitor staurosporine. We propose that TPPII participates in apoptotic pathways.

Acetylcysteine↗
PubMed2000

Salmonella enterica serovar typhimurium peptidase B is a leucyl aminopeptidase with specificity for acidic amino acids.

Peptidase B (PepB) of Salmonella enterica serovar Typhimurium is one of three broad-specificity aminopeptidases found in this organism. We have sequenced the pepB gene and found that it encodes a 427-amino-acid (46.36-kDa) protein, which can be unambiguously assigned to the leucyl aminopeptidase (LAP) structural family. PepB has been overexpressed and purified. The active enzyme shows many similarities to other members of the LAP family: it is a heat-stable (70 degrees C; 20 min) hexameric ( approximately 270-kDa) metallopeptidase with a pH optimum of 8.5 to 9.5. A detailed study of the substrate specificity of the purified protein shows that it differs from other members of the family in its ability to hydrolyze peptides with N-terminal acidic residues. The preferred substrates for PepB are peptides with N-terminal Asp or Glu residues. Comparison of the amino acid sequence of PepB with those of other LAPs leads to the conclusion that PepB is the prototype of a new LAP subfamily with representatives in several other eubacterial species and to the prediction that the members of this family share the ability to hydrolyze peptides with N-terminal acidic residues. Site-directed mutagenesis has been used to show that this specificity appears to be determined by a single Lys residue present in a sequence motif conserved in all members of the subfamily.

Amino Acid Sequence↗
PubMed2005

Mitotic infidelity and centrosome duplication errors in cells overexpressing tripeptidyl-peptidase II.

The oligopeptidase tripeptidyl-peptidase II (TPP II) is up-regulated Burkitt's lymphoma (BL) cells that overexpress the c-myc proto-oncogene and is required for their growth and survival. Here we show that overexpression of TPP II induces accelerated growth and resistance to apoptosis in human embryonic kidney 293 cells. This correlates with the appearance of multiple chromosomal aberrations, numerical and structural centrosome abnormalities, and multipolar cell divisions. Similar mitotic aberrations were also observed in a panel of BL lines and were suppressed, in parallel with TPP II down-regulation, upon reversion of BL-like characteristics in EBV-immortalized B lymphocytes carrying a tetracycline-regulated c-myc. Functional TPP II knockdown by small interfering RNA expression in BL cells caused the appearance of giant polynucleated cells that failed to complete cell division. Collectively, these data point to a role of TPP II in the regulation of centrosome homeostasis and mitotic fidelity suggesting that this enzyme may be a critical player in the induction and/or maintenance of genetic instability in malignant cells.

Aminopeptidases↗
PubMed1984

Heterogeneous expression of dipeptidyl-amino-peptidase (DAP IV) in T-cell chronic lymphocytic leukemia.

The reactivity for the enzyme dipeptidyl-amino-peptidase IV (DAP IV) has been correlated, in 8 cases of T-cell chronic lymphocytic leukemia (T-CLL), with the cellular phenotype as well as the morphological and clinical behaviour of disease. A highly reproducible correspondence between the 'helper' phenotype (OKT4+/Fc mu-R+) and DAP IV expression was observed in cases with aggressive disease, whereas the cases with OKT8+/Fc mu-R+ phenotype was characterized by a favorable prognosis, LGL (large granular lymphocyte) morphology, and were virtually negative for DAP IV.

Adult↗
PubMed1996

A novel heparin-dependent processing pathway for human tryptase. Autocatalysis followed by activation with dipeptidyl peptidase I.

Tryptase is the major protein constituent of human mast cells, where it is stored within the secretory granules as a fully active tetramer. Two tryptase genes (alpha and beta) are expressed by human mast cells at the level of mRNA and protein, each with a 30 amino acid leader sequence. Recombinant precursor forms of human alpha- and beta-tryptase were produced in a baculovirus system, purified, and used to study their processing. Monomeric beta-protryptase first is shown to be intermolecularly autoprocessed to monomeric beta-pro'tryptase at acid pH in the presence of heparin by cleavage between Arg-3 and Val-2 in the leader peptide. The precursor of alpha-tryptase has an Arg-3 to Gln-3 mutation that precludes autoprocessing. this may explain why alpha-tryptase is not stored in secretory granules, but instead is constitutively secreted by mast cells and is the predominant form of tryptase found in blood in both healthy subjects and those with systemic mastocytosis under nonacute conditions. Second, the NH2-terminal activation dipeptide on beta-pro'tryptase is removed by dipeptidyl peptidase I at acid pH in the absence of heparin to yield an inactive monomeric form of tryptase. Conversion of the catalytic portion of beta-tryptase to the active homotetramer at acid pH requires heparin. Thus, beta-tryptase homotetramers probably account for active enzyme detected in vivo. Also, processing of tryptase to an active form should occur optimally only in cells that coexpress heparin proteoglycan, restricting this pathway to a mast cell lineage.

Amino Acid Sequence↗
PubMed1981

Fluorescence demonstration of dipeptidyl peptidase II in skeletal, cardiac, and vascular smooth muscles.

Dipeptidyl peptidase II (Dpp II) was demonstrated histochemically in soleus, extensor digitorum longus, cardiac, and vascular smooth muscle tissues using Lys-Ala-4-methoxy-beta-naphthylamide or Lys-Pro-4-methoxy-beta-naphthylamide as the substrate. The enzyme was found to be localized in discrete granules in all muscle types, but varied in its apparent activity. Dpp II activity was greatest in cardiac and least in extensor digitorum longus muscles with activity in soleus and vascular smooth muscles in between these extremes. Since Dpp II is localized only in lysosomes, the relative amounts and locales of lysosomes can be easily observed in normal muscle cells by the techniques described in this study.

Animals↗