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:3.1.3.1 (alkaline phosphatase)
47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The vitamin A derivative retinoic acid (RA) is widely thought to be involved in cartilage development, but its precise roles and mechanisms of action in this complex process remain unclear. We have tested the hypothesis that RA is involved in chondrocyte maturation during endochondral ossification and, in particular, is an inducer of maturation-associated traits such as type X collagen and alkaline phosphatase. Immature chondrocytes isolated from the caudal region of Day 19 chick embryo sterna were seeded in secondary monolayer cultures and treated either with a high dose (100 nM) or with physiological doses (10-35 nM) of RA for up to 3 days. We found that after an initial lag of about 24 h, physiological doses of RA indeed induced type X collagen gene expression in the immature cells. This induction was not accompanied by obvious changes in expression of the type II collagen and large aggregating proteoglycan core protein genes. As revealed by immunocytochemistry, 30-35% of the cells in cultures treated with RA for 3 days were engaged in type X collagen production. Interestingly, these cells were relatively similar in size to chondrocytes in which no type X collagen was detected, suggesting that chondrocytes can initiate type X collagen production independent of cell hypertrophy. RA treatment also led to increased alkaline phosphatase activity occurring as early as 24 h after the start of treatment. The data in this study indicate that RA may have a role in endochondral ossification as an inducer/promoter of maturation-associated traits during chondrocyte maturation.
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PMID:Retinoic acid treatment induces type X collagen gene expression in cultured chick chondrocytes. 205 74

Monoclonal antibodies (MAbs) were raised against gag proteins of human immunodeficiency virus type 1 (HIV-1), strain HTLV-IIIB. One of 29 antibodies was specific for p17 of HIV-1. Twenty of 28 MAbs reactive with the major core protein p24 of HIV-1 showed cross-reactivity with HIV-2, and five of these also detected the corresponding antigens of simian immunodeficiency virus (SIVmac). The MAbs were reactive in several tests, i.e. ELISA, immunostaining of Western blots, immunofluorescence, alkaline phosphatase-anti-alkaline phosphatase immunocytochemistry and immunoelectron microscopy. The submembrane protein p17 was clearly localized within the virion.
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PMID:Monoclonal antibodies directed against human immunodeficiency virus (HIV) gag proteins with specificity for conserved epitopes in HIV-1, HIV-2 and simian immunodeficiency virus. 245 67

Heparan sulfate proteoglycans (HSPG) of rat liver are associated with the plasma membrane in a hydrophobic intrinsic and a hydrophilic extrinsic form. We were interested in determining whether or not these two forms could be detected in the Golgi apparatus, the subcellular site of addition of oligosaccharides and sulfate to HSPG. In vivo and in vitro radiolabeled HSPG from rat liver Golgi apparatus membranes could only be solubilized with detergents that disrupt the membrane lipid bilayer, suggesting that they are solely associated via hydrophobic interactions. Both forms of HSPG were detected in plasma membranes of rat liver and isolated rat hepatocytes. The detergent-solubilized HSPG bound to octyl-Sepharose columns, whereas the hydrophilic form did not; this latter form, however, was released from the membrane by heparin. The hydrophobic anchor of HSPG in the Golgi and plasma membranes was insensitive to treatment with phosphatidylinositol-specific phospholipase C under conditions in which alkaline phosphatase was sensitive; this suggests that the hydrophobic anchor of HSPG is the core protein itself. Preliminary experiments suggest that the subcellular site of processing of the hydrophobic to the hydrophilic form of HSPG is the plasma membrane. A specific processing activity, probably a protease of the plasma membrane not present in serum or the endoplasmic reticulum membrane, converted hydrophobic HSPG of the Golgi membrane to the hydrophilic form. In addition, pulse-chase experiments with [35S]Na2SO4 in rats demonstrated that at short times, the bulk of the radiolabeled cellular HSPG was in the Golgi apparatus; later on, the bulk of the radioactivity was found in the plasma membrane, the only subcellular site where the hydrophilic form of HSPG was detected.
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PMID:Differential association of rat liver heparan sulfate proteoglycans in membranes of the Golgi apparatus and the plasma membrane. 252 26

Purified proteoglycan subunits from human articular, bovine articular and nasal cartilages, and a rat chondrosarcoma were phosphorylated in vitro by beef heart cAMP-dependent protein kinase in the presence of gamma 32P-ATP. In these experiments, a maximum of 1.7 moles of 32P were incorporated per mole of proteoglycan from human cartilage. Phosphorylation was dependent on the presence of cAMP. Analysis by autoradiography revealed that serine residues in the core protein of the proteoglycan were the sites of phosphorylation. Treatment of proteoglycan subunits with chondroitinase ABC and alkaline phosphatase prior to reaction with cAMP-dependent protein kinase increased the incorporation of 32P by 12-30% when compared with untreated proteoglycans. These data indicate that proteoglycans in cartilage can be phosphorylated by cAMP-dependent protein kinase.
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PMID:Phosphorylation of proteoglycans from human articular cartilage by a cAMP-dependent protein kinase. 647 53

The nature of the protein kinase (PK) which phosphorylates the core protein of hepatitis B virus in vitro was studied. The PK copurified with the core particles during rate zonal centrifugation and gel chromatography. It showed the same size heterogeneity as the core particles, which consisted of a main fraction of 28-nm particles and a subfraction of 22- to 26-nm particles. DNA-containing heavy core particles with a density of 1.33 to 1.35 g/ml and less endogenous PK than did the light cores. The phosphorylation reaction had a rapid initial phase (several minutes) and a slow but long-lasting second phase (many hours). The PK had a high affinity for ATP (KM = 0.5 mumol/liter). Only few of the several hundred P21.9 subunits in one core particle were phosphorylated in vitro. The only amino acid which was phosphorylated in vitro was serine. The resistance of the introduced phospho group against alkaline phosphatase showed that the PK acceptor, and probably the enzyme itself, was located inside the core particle.
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PMID:Specificity and localization of the hepatitis B virus-associated protein kinase. 680 56

To determine the prevalence and clinical significance of IgM and IgA antibody to hepatitis C virus (HCV) core antigen in chronic HCV infection, sera from 47 patients were tested for immunoglobulin class M (IgM) and immunoglobulin A (IgA) antibody to HCV core antigen by solid-phase enzyme-linked immunoassay using a recombinant core protein (aa1-150). Results were correlated with the clinical, biochemical and histological parameters, serum HCV RNA levels (determined by branched DNA signal amplification assay), and subsequent clinical response to interferon-alpha therapy. IgM anti-HCV core was detected in 11 patients (23.4 percent). There was no correlation between the presence of IgM anti-HCV core and the clinical features (sex, age, mode of acquisition), biochemical parameters (serum ALT, AST, alkaline phosphatase, and albumin level), autoimmune markers [serum globulin levels, anti-nuclear antibody (+ at < 1:80 in 7/47 patients)], serum HCV RNA levels, subsequent response to interferon-alpha therapy, and the histological features. Immunoglobulin A anti-HCV core was not detected in any of the patients. The presence of IgM ant-HCV core in a proportion of patients with chronic HCV infection indicates that the presence of serum IgM anti-HCV core may not be unique to acute HCV infection.
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PMID:Immunoglobulin M and A antibodies to hepatitis C core antigen in chronic hepatitis C virus infection. 752 59

Binding and signaling proteins based on Escherichia coli alkaline phosphatase (AP; EC 3.1.3.1) were designed for the detection of antibodies. Hybrid proteins were constructed by using wild-type AP and point mutants of AP [Asp-101 --> Ser (D101S) and Asp-153 --> Gly (D153G)]. The binding function of the hybrid proteins is provided by a peptide epitope inserted between amino acids 407 and 408 in AP. Binding of anti-epitope antibodies to the hybrid proteins modulates the enzyme activity of the hybrids; upon antibody binding, enzyme activity can increase to as much as 300% of the level of activity in the absence of antibody or can decrease as much as 40%, depending on the presence or absence of the point mutations in AP. The fact that modulation is altered from inhibition to activation by single amino acid changes in the active site of AP suggests that the mechanism for modulation is due to structural alterations upon antibody binding. Modulation is a general phenomenon. The properties of the system are demonstrated by using two epitopes, one from the V3 loop of human immunodeficiency virus type 1 gp120 protein and one from hepatitis C virus core protein, and corresponding monoclonal antibodies. The trend of modulation is consistent for all hybrids; those in wild-type AP are inhibited by antibody, while those in the AP mutants are activated by antibody. This demonstrates that modulation of enzyme activity of the AP-epitope hybrid proteins is not specific to either a particular epitope sequence or a particular antibody-epitope combination.
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PMID:A molecular sensor system based on genetically engineered alkaline phosphatase. 754 Nov 35

The present work was to study the quantitative change of proteoglycan (PG) in homogenous cartilage graft in the guinea pig. Histological, histochemical and biochemical studies were undertaken at different times after grafting. The results revealed that there was a marked reducing trend of matrix PG within four weeks after grafting. Four weeks afterwards all indexes except hexuronic acid restored slowly and approached the level of the control group. By the 20th week, the activity of neutromucopolysaccharide, hexosamine, acid-mucopolysaccharide and alkaline phosphatase restored to 73.6% -93.7% of the control group (P > 0.05). The changes probably were caused by immune reaction and operative trauma. PG in the cartilage matrix forms a barrier for the chondrocytes, protecting the host's immune system from contacting and reacting with the chondrocytes of the graft. Though the core protein of PG has antigenicity, it is surrounded by acidmucopolysaccharide that has no antigenicity. We concluded that it is very important to maintain a high level of PG in order to prolong the survival of a cartilage graft.
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PMID:[Experimental observations of the quantitative changes of proteoglycan in homogenous cartilage graft in the guinea pig]. 764 1

A chondroitin sulfate-dermatan sulfate proteoglycan was isolated from bovine aorta intima by extraction of the tissue with 4 M guanidine hydrochloride. The proteoglycan was purified by CsCl isopycnic centrifugation followed by gel filtration and ion exchange chromatography. A monoclonal antibody C8F4 was developed to this core protein. The characteristics and specificity of the antibody were studied by an enzyme-linked immunosorbent assay (ELISA) using an alkaline phosphatase conjugated antibody (goat anti-mouse IgG). The antibody binding to the core protein was found specific and optimal at pH 7.0. The antibody recognizes either intact chondroitin sulfate-dermatan sulfate proteoglycan monomer, chondroitinase ABC digested monomer or chemically deglycosylated proteoglycan. Free chondroitin sulfates, keratan sulfate and hyaluronic acid did not compete for the antigenic sites in ELISA. Limited hydrolysis of the core protein by trypsin resulted in three peptides and only the peptide with a molecular weight M(r) = 40,000 was found capable of binding to hyaluronic acid. The antibody C8F4 recognized this hyaluronic acid binding peptide but did not recognize the other two peptides suggesting that the epitope(s) for this antibody is in the hyaluronic acid-binding region of the core protein. The antibody recognized the core proteins from bovine nasal cartilage proteoglycan and human aorta proteoglycan but did not recognize bovine aorta link protein, bovine serum albumin, human serum albumin, human transferrin, collagen Type I and fibronectin. The antibody was found useful to localize proteoglycans in atherosclerotic lesions in human aorta by immunohistochemical techniques.
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PMID:A monoclonal antibody that recognizes hyaluronic acid binding region of aorta proteoglycans. 768 Dec 90

Endochondral bone formation occurs by a series of developmentally regulated cellular events from initial formation of cartilage tissue to stages of calcified cartilage, resorption, and replacement by bone tissue. Several studies have raised the question of the possibility that the hypertrophic chondrocytes associated with the calcifying cartilage matrix can acquire properties similar to osteoblasts. We have addressed this possibility by measuring synthesis within hypertrophic chondrocytes in vitro of two bone-related proteins, osteopontin and osteocalcin. Chondrocytes derived from chick embryo ventral vertebral tissue were cultured under conditions that promoted extracellular matrix mineralization and differentiation towards the hypertrophic phenotype as indicated by the induction of Type X collagen, alkaline phosphatase, and diminished expression of Type II collagen and the core protein of large proteoglycan. In these cultures, osteopontin synthesis was detected in early cultures in the absence of a calcified matrix; in contrast, an absence of the bone-specific protein osteocalcin was observed. However, with onset of development of the hypertrophic phenotype an induction of protein expression for osteocalcin was observed with a significant (twofold) increase in osteopontin. Maximal levels of osteocalcin synthesis occurred with the peak of alkaline phosphatase activity and Type X collagen mRNA levels. The levels of osteocalcin synthesis were induced fiftyfold from the earliest level of detection but this level was only one one-hundredth of that observed for mature chick osteoblast cultures. Osteocalcin and osteopontin were characterized by several criteria (electrophoresis, immunoblotting, chromatographic characteristics, and response to 1,25(OH)2D3) which confirmed their molecular properties as being identical to osteoblast synthesized proteins. The coordinate change in the cellular phenotype to the hypertrophic chondrocyte was shown to be concurrent with ultrastructural maturation of the cells and the accumulation of osteocalcin and osteopontin in the extracellular matrix associated with hydroxyapatite at sites of mineralization. Since the ultrastructural features of the cells in vitro and the extracellular matrix surrounding the lacunae have features of the hypertrophic chondrocyte and associated matrix in vivo, the induction of the bone-specific protein osteocalcin suggests that at least a population of these cells may develop osteoblastic phenotypic markers in association with mineralizing matrix. The detection of osteocalcin and the high level of synthesis of osteopontin may represent an advanced stage of chondrocyte hypertrophy or the possibility of a trans-differentiation of the chondrocytes to an osteoblastic-like cell.
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PMID:Induction of bone-related proteins, osteocalcin and osteopontin, and their matrix ultrastructural localization with development of chondrocyte hypertrophy in vitro. 836 37


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