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:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A very high molecular weight mucin-like glycoprotein was isolated by gel filtration of interphotoreceptor matrix (IPM) from fresh bovine eyes and purified to apparent homogeneity by cesium chloride/guanidine hydrochloride (GuHCl) equilibrium density gradient centrifugation. Although a molecular weight in excess of 10(7) Da is suggested by gel filtration, the presence of SDS or GuHCl did not alter its elution position, indicating that the large size was not simply due to aggregation. Treatment of this material with disulfide reagents, however, led to a decrease in molecular size. On a relative basis, substantially more of this glycoprotein is present in IPM prepared from retina than from retinal pigment epithelium. While the carbohydrate and amino acid composition are not those of a true 'mucin', the large size and many other properties are quite 'mucin-like'. The carbohydrate composition suggests the presence of both N- and O-glycosidically linked sugar chains. The presence of a mucin-type O-glycosidic linkage is indicated by its susceptibility to alkaline cleavage, with concomitant loss of serine and threonine and increase in 240 nm absorbance; production of a fluorescent product upon reaction with cyanoacetamide; lectin binding properties; and production of N-acetylgalactosaminitol upon alkaline borohydride elimination. This glycoprotein was digested by pronase and trypsin, confirming its protein nature, but was resistant to digestion with chondroitin ABC lyase, hyaluronidase and heparinase, as well as RNAase, indicating that these components were not present to any appreciable extent. ELISA for cartilage keratan sulfate was also negative. Centrifugation in CsCl/GuHCl gradients indicated a density much lower than that of a proteoglycan or nucleic acid as well. In vitro biosynthetic studies suggest that both retina and retinal pigment epithelium may be major sources of material in the IPM. The elution patterns of radioactivity were strikingly similar to the UV elution patterns of IPM. The medium from retinal incubations contained very high molecular weight material which was resistant to enzymes which hydrolyse glycosaminoglycans, suggesting that retina may be the source of this high molecular weight, mucin-like glycoprotein.
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PMID:High molecular weight mucin-like glycoproteins of the bovine interphotoreceptor matrix. 154 29

Neutral proteolytic activity, having a pH optimum of about 7, was present in the high molecular weight fraction of bovine interphotoreceptor matrix (IPM) separated by gel filtration on Sephacryl S-500. The enzyme(s) was active toward a number of exogenous substrates, including albumin, Azocoll, and gelatin. However, it was inactive toward a synthetic substrate for bacterial collagenase. Proteolytic activity was proportional to protein; however, the time course of the reaction was nonlinear, suggesting that "activation" of a precursor form might be necessary. Of a number of specific inhibitors tested, those directed toward metalloproteinases (1,10-phenanthroline greater than EDTA greater than EGTA) proved most effective. While activity was also inhibited by sulfhydryl reagents and dithiothreitol, inhibitors specific for cysteine proteinases were ineffective. Higher specific activity was present in IPM obtained from retinal pigment epithelium (RPE) than from retina. An endogenous proteinase inhibitor(s) was also found in IPM from both RPE and retina. It was effective against the endogenous metalloproteolytic activity of IPM and also against thermolysin, but not against trypsin or papain. Fractionation of IPM on Sephacryl S-500 revealed a broad peak of inhibitory activity at molecular weights of less than 10(5) daltons. This is the first report of the presence of neutral proteolytic activity and metalloproteinase inhibitor(s) in bovine IPM. These materials may function in concert to maintain the proper level of various components within this matrix.
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PMID:The presence of neutral metalloproteolytic activity and metalloproteinase inhibitors in the interphotoreceptor matrix. 155 92

A phosphodiesterase (PDE) has been characterized in the interphotoreceptor matrix (IPM) of light-adapted fresh bovine retinas. It is obtained through a gentle rinsing of the retinal surface under conditions where the light-activated rod outer segment (ROS) enzyme remains attached. The enzyme has an apparent native molecular weight of 350 000 by gel filtration and appears as a doublet at Mr 47 000 and 45 000 on sodium dodecyl sulfate-polyacrylamide gels. It has an apparent Km value for cGMP of 33 microM and an apparent Km value for cAMP of 2200 microM. It is activated 3-6-fold by protamine and over 40-fold by trypsin. Protamine has no effect on the Km for cGMP while trypsin decreases the Km for cGMP by a factor of 2. The enzyme occurs in at least two forms as evidenced by two distinct peaks of activity after gel electrophoresis under nondenaturing conditions. A heat-stable inhibitor is tightly bound to the enzyme. The inhibitor obtained from the IPM PDE inhibits 98% of the activity of the trypsin-activated ROS PDE: conversely, the inhibitor obtained by boiling the ROS PDE completely inhibits the trypsin-activated IPM enzyme. A high-affinity monoclonal antibody to the active site of the ROS PDE, ROS 1 [Hurwitz, R., Bunt-Milan, A.H., & Beavo, J. (1984) J. Biol. Chem. 259, 8612-8618], quantitatively absorbs the IPM PDE. These observations indicate a clear relationship between these two PDEs even though their location, sizes, and specific functions in the retina appear to be distinct.
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PMID:Extracellular cGMP phosphodiesterase related to the rod outer segment phosphodiesterase isolated from bovine and monkey retinas. 298 11

The retinal interphotoreceptor matrix (IPM) occupies the space between the neural retina and the retinal pigmented epithelium (RPE), two neuroectoderm-derived epithelia. While the IPM appears to be a major route by which photoreceptor cells receive vital metabolic factors, relatively little is known concerning its structure and function. The studies reported here describe the presence of specialized domains of the IPM that ensheath cone, but not rod, inner and outer segments in pig, monkey, and human retinae. These cone extracellular matrix sheaths are chemically and structurally distinct from the remainder of the IPM as revealed by their specific binding of the lectin peanut agglutinin (PNA) and their structural stability during physical dissociation of the retina. Biochemical studies suggest that the PNA-binding components of the cone matrix sheaths are trypsin-sensitive glycoproteins. These structures may play a role in establishing a specialized microenvironment for cone photoreceptors, maintaining proper orientation of cone outer segments, and/or facilitating cone-RPE interactions.
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PMID:Interphotoreceptor matrix domains ensheath vertebrate cone photoreceptor cells. 308 Mar 82

Characteristics of the chondroitin sulfate/dermatan sulfate proteoglycans (CS/DSPGs) and heparan sulfate proteoglycans (HSPGs) from retinas of 14-day chicken embryos were examined following specific lyase digestion of the HSPG and CS/DSPG glycosaminoglycans, respectively. On the basis of gel exclusion chromatography the prevalent CS/DSPGs in the tissue were above Mr 400 X 10(3) with two or three glycosaminoglycan chains of Mr 60-70 X 10(3). The HSPGs existed in two distinct populations in the tissue. Those in the dominant population appeared to be in the range of Mr 250-300 X 10(3) with 9 to 12 glycosaminoglycan chains of Mr 15-25 X 10(3). The other population consisted of free heparan sulfate chains of Mr 15-25 X 10(3). The HSPGs in the medium tended to be intermediate in size. To examine the distribution of proteoglycans, tissues were sequentially homogenized and extracted in saline and reextracted with 4 M guanidine HCl (GdnHCl) and Triton X-100 (TX), or they were washed in heparin solution and dissociated to single cells with trypsin before sequential extraction in saline and GdnHCl with TX. Through comparison of the results of these two extraction methods, CS/DSPGs were found to be almost entirely within the medium or matrix or loosely associated with the cell surface, and most HSPGs were associated with either the basal lamina or the plasma membrane. The single heparan sulfate glycosaminoglycan chains appeared to be intracellular degradation products. These results support reports that CS/DSPGs may be present in the retina interphotoreceptor matrix and that HSPGs may be present in regions of synaptogenesis, associated with cell membranes.
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PMID:Proteoglycans synthesized by embryonic chicken retina in culture: composition and compartmentalization. 311 39

Enzyme-linked lectin cytochemical and biochemical analyses have been used to identify microdomains of retinal outer segments and interphotoreceptor matrix glycoconjugates. We have devised a highly reproducible trypsin digestion procedure to identify protease-resistant wheat germ agglutinin (WGA) domains on the distal tips of some photoreceptor outer segments, and on shed outer segment membrane in Xenopus laevis retina. WGA binding sites in the frog interphotoreceptor matrix were completely susceptible to trypsin digestion. In contrast, the cytochemical procedures revealed a distinct protease resistant WGA-positive microdomain in the interphotoreceptor matrix of rat (and probably human) retina at the outer segment-pigment epithelium interface. Neuraminidase digestion of sections of rat retina previously digested with trypsin essentially completely removed WGA binding sites in this microdomain. These results indicated that the protease-resistant carbohydrates were sialoglycoconjugates. A potential role for this pool of sialoglycoconjugates would be to mediate adhesion of the outer segment-pigment epithelium interface. Analysis of solubilized retina digested with trypsin and separated by polyacrylamide gel electrophoresis revealed a set of protease resistant WGA binding glycoprotein of Mr 60 kDa on nitrocellulose transblots which we hypothesize may be a component of the protease resistant microdomain at the outer segment-pigment epithelium interface of rat retina.
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PMID:Microenvironments of photoreceptor and interphotoreceptor matrix glycoconjugates. 355

A model system for retinal adhesion, consisting of interacting bovine pigment, epithelium (PE) cells and photoreceptor outer segments, was utilized to examine any adhesive role of the interphotoreceptor matrix. PE cells were dissociated by trypsin treatment of the eyecup, and were allowed to replenish their surface proteins as single cells in spinner culture. They were then placed into short-term, slowly rotating suspension cultures, where their rapid aggregation as a function of time could be studied. Outer segments exhibited no tendency to interact with one another, or with PE cells, in suspension culture. Extracellular interphotoreceptor matrix from adult bovine eyes was isolated by rinsing the apposing surfaces of neural retina and PE. When this matrix material was added to the cell suspension cultures, adhesion between PE cells and outer segments in mixed cultures was not enhances. However, PE reaggregation itself appeared to be augmented. The principal matrix glycoprotein, obtained by concanavalin A affinity chromatography, displayed adhesive properties similar to those of the interphotoreceptor matrix. Thus, under the conditions of these in vitro experiments, no evidence could be obtained that either cell surface molecules or interphotoreceptor matrix plays a role in retinal adhesion.
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PMID:Interaction of bovine pigment epithelium cells, photoreceptor outer segments, and interphotoreceptor matrix: a model for retinal adhesion. 734 30

To identify soluble proteins of the retinal interphotoreceptor matrix (IPM), we isolated IPM from the bovine eye by gentle lavage and subjected it to SDS-PAGE. In the resultant gel, a 46 kDa band was particularly prominent and appeared to be a single protein. This protein was electroblotted to nitrocellulose membrane, digested with trypsin, and selected peptides were isolated by HPLC and subjected to Edman microsequencing. The amino acid sequences of the peptides were found to be virtually identical to that of human neuron-specific enolase (NSE). A monoclonal antibody specific for human NSE confirmed the presence of this enzyme in the bovine IPM by both Western blotting and immunocytochemical analysis. Immunofluorescence microscopy demonstrated that NSE is mainly localized to the basal domain of the IPM surrounding photoreceptor cells but is also prominent in the inner segments of the cone photoreceptor neurons. When NSE was added to cultures of human retinoblastoma cells, no effect on morphology was observed. However, a positive effect on cell growth and/or survival was readily apparent. It thus seems that not only is NSE a significant component of the retinal extracellular matrix, but that it could function as a survival (neuronotrophic) factor for photoreceptor neurons.
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PMID:Neuron-specific enolase: a neuronal survival factor in the retinal extracellular matrix? 782 43

The distribution of hyaluronan (HA) in the posterior eye wall from the vitreous through the sclera, with special consideration to localization in the retina and interphotoreceptor matrix (IPM), was evaluated in mouse tissues using an HA specific probe (bHABC, biotinylated hyaluronan binding complex). The vitreous body was positive for HA, as was Bruch's membrane, expansive areas within the choroid, sclera and perimysial connective tissue of extraocular muscle. No HA-staining was detected in the IPM or in any other retina layer except for the basal lamina (inner limiting membrane of the retina) which abuts the vitreous. Predigestion of sections with trypsin or chondroitinase ABC before bHABC application did not produce additional HA-staining in the retina or IPM.
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PMID:Hyaluronan localization in tissues of the mouse posterior eye wall: absence in the interphotoreceptor matrix. 936 40

Mouse SPACR cDNA was cloned by screening a mouse retina cDNA library using a PCR probe derived from human SPACR cDNA. Mouse SPACR cDNA comprises 3675 bp containing an open reading frame coding for 742 amino acids. Multitissue Northern blot analysis and in situ hybridization studies indicate that SPACR expression is restricted to retinal photoreceptors. The SPACR core protein was identified with Western blotting following SDS-PAGE with a SPACR C-terminal peptide polyclonal antibody and a chondroitin-6-sulfate Deltadisaccharide monoclonal antibody. The 150 kD immunopositive band was isolated, digested with trypsin and the peptides analysed by MALDI mass spectroscopy. Peptide mass mapping confirmed the identity of the 150 kD immunopositive band to be mouse SPACR core protein. Alignment comparisons of the deduced amino acid sequence of mouse and human SPACR show 64% homology. Like SPACR in the human interphotoreceptor matrix, the mouse orthologue contains a large central mucin-like domain flanked by consensus sites for N-linked oligosaccharide attachment, one EGF-like domain and four hyaluronan-binding motifs. Unlike human SPACR, which contains no conventional consensus sites for glycosaminoglycan attachment, mouse SPACR contains three. Recent biochemical studies of human and mouse SPACR protein indicate that this novel interphotoreceptor matrix molecule is a glycoprotein in human and a proteoglycan in the mouse. The presence of consensus sites for glycosaminoglycan attachment in the deduced sequence of mouse SPACR and the absence of these sites in human SPACR provide molecular verification of our biochemical results, suggesting that differences in post-translational modifications of SPACR may be important in SPACR function in foveate and non-foveate retinas.
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PMID:SPACR in the interphotoreceptor matrix of the mouse retina: molecular, biochemical and immunohistochemical characterization. 1099 55


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