Tartrate-inhibitable acid phosphatase. Purification from placenta, characterization and subcellular distribution in fibroblasts

Tartrate-inhibitable acid phosphatase was purified to apparent homogeneity from human placenta. The enzyme is composed of two subunits with an apparent molecular mass of 48 kDa. Each subunit carries one oligosaccharide of the high-mannose/hybride type. The purified enzyme has an isoelectric point of pH 6.2. It cleaves phosphomonoester bonds at acid pH, is competitively inhibited by L-tartrate, Ki = 0.51 microM, and phosphate, Ki = 0.8mM. A monospecific antiserum raised against the purified placental enzyme precipitated 62% and 85% of the tartrate-inhibitable acid phosphatase present in extracts of placenta and fibroblasts, respectively. By means of subcellular fractionation and immunoprecipitation it was shown that the majority of tartrate-inhibitable acid phosphatase is located in lysosomes in normal and mucolipidosis II fibroblasts. In the human Hep G-2 hepatoma cells a significant fraction of the enzyme appears to be associated with non-lysosomal organelles.     

Comparison of human alkaline phosphatase isoenzymes. Structural evidence for three protein classes.

The structural relationships among human alkaline phosphatase isoenzymes from placenta, bone, kidney, liver and intestine were investigated by using three criteria. 1. Immunochemical characterization by using monospecific antisera prepared against either the placental isoenzyme or the liver isoenzyme distinguishes two antigenic groups: bone, kidney and liver isoenzymes cross-react with anti-(liver isoenzyme) serum, and the intestinal and placental isoenzymes cross-react with the anti-(placental isoenzyme) antiserum. 2. High-resolution two-dimensional electrophoresis of the 32P-labelled denatured subunits of each enzyme distinguishes three groups of alkaline phosphatase: (a) the liver, bone and kidney isoenzymes, each with a unique isoelectric point in the native form, can be converted into a single form by treatment with neuraminidase; (b) the placental isoenzyme, whose position also shifts after removal of sialic acid; and (c) the intestinal isoenzyme, which is distinct from all other phosphatases and is unaffected by neuraminidase digestion. 3. Finally, we compare the primary structure of each enzyme by partial proteolytic-peptide 'mapping' in dodecyl sulphate/polyacrylamide gels. These results confirm the primary structural identity of liver and kidney isoenzymes and the non-identity of the placental and intestinal forms. These data provide direct experimental support for the existence of at least three alkaline phosphatase genes.     

Aldose and aldehyde reductases in human tissues

Immunochemical characterizations of aldose reductase and aldehyde reductases I and II, partially purified by DEAE-cellulose (DE-52) column chromatography from human tissues, were carried out by immunotitration, using antisera raised against the homogenous preparations of human and bovine lens aldose reductase and human placenta aldehyde reductase I and aldehyde reductase II. Anti-aldose reductase antiserum cross-reacted with aldehyde reductase I, anti-aldehyde reductase I antiserum cross-reacted with aldose reductase and anti-aldehyde reductase II antiserum precipitated aldehyde reductase II, but did not cross-react with aldose reductase or aldehyde reductase I from all the tissues examined. DE-52 elution profiles, substrate specificity and immunochemical characterization indicate that aldose reductase is present in human aorta, brain, erythrocyte and muscle; aldehyde reductase I is present in human kidney, liver and placenta; and aldehyde reductase II is present in human brain, erythrocyte, kidney, liver, lung and placenta. Monospecific anti-α and anti-β antisera were purified from placenta anti-aldehyde reductase I antiserum, using immunoaffinity techniques. Anti-α antiserum precipitated both aldehyde reductase I and aldose reductase, whereas anti-β antibodies cross-reacted with only aldehyde reductase I. Based on these studies, a three gene loci model is proposed to explain the genetic interrelationships among these enzymes. Aldose reductase is a monomer of α subunits, aldehyde reductase I is a dimer of α and β subunits and aldehyde reductase II is a monomer of δ subunits.     

Biosynthesis and processing of lysosomal acid phosphatase in cultured human cells

The biosynthesis of lysosomal acid phosphatase was studied in a normal human embryonic lung cell line, WI-38. Cells were labeled with radioactive leucine under a variety of conditions, the enzyme was immunoprecipitated using a monospecific antiserum raised against human liver lysosomal acid phosphatase, and the products were separated by electrophoresis and were visualized by fluorography. Lysosomal acid phosphatase constitutes 60% of the total tartrate-inhibitable acid phosphatase in WI-38. It is initially synthesized as a high-molecular-weight precursor polypeptide of 69 kDa. The precursor polypeptide is rapidly glycosylated and processed to a mature enzyme of 53-45 kDa via intermediates of 65 and 60 kDa in WI-38 cells. The 69-kDa precursor polypeptide is also converted to larger precursor polypeptides of 74 and 80 kDa. The multiplicity of precursor polypeptides is due at least in part to differences in the glycosylation and phosphorylation of the polypeptides. Sensitivity of phosphorylated oligosaccharide chains from precursor, mature and small polypeptides to endo-beta-hexosaminidase H-catalyzed cleavage suggests the presence of high-mannose phosphorylated oligosaccharide chains similar to those present on many other lysosomal enzymes. The effects of tunicamycin and ammonium chloride were also studied. In contrast to the effect of ammonium chloride on arylsulfatase A secretion, the lysosomal acid phosphatase in WI-38 cells was not secreted in the presence of NH4Cl. This is consistent with the existence of an alternate route for the transfer of lysosomal acid phosphatase into lysosomes. This alternate route may be the reason that I-cell fibroblasts contain a normal level of lysosomal acid phosphatase.     

Characterization of antigenic sialoglycoprotein subunits of the placental brush border membranes: Comparison with liver and kidney membrane subunits by two-dimensional electrophoresis

The sialoglycoprotein subunits of human placental brush border membranes were labeled by sequential treatment with periodate and (³H)-sodium borohydride, which trititates sialic acid, and by lactoperoxidase-catalyzed (¹²⁵I) iodination of tyrosine residues. The labeled subunits were characterized with respect to their affinity for antisera raised against Triton X-100 extracts of placental brush border membranes. The immunochemically reactive components were analyzed by two-dimensional electrophoresis according to a modification of the O'Farrell technique [20] enabling the assignment of estimated M_r? and pI. Of the 33 ³H-labeled brush border subunits present in Triton X-100-solubilized membrane preparations, 18 subunits reacted with antiplacental brush border antisera insolubilized on CNBr-activated Sepharose or in immunoprecipitates. Fourteen of these tritiated subunits were also labeled with ¹²⁵I, confirming that these are glycoproteins. The plasma membranes of normal human liver and microsomes from kidney were examined for the placental brush border glycoprotein subunits by reaction with insolubilized antiplacental brush border antisera and two-dimensional electrophoresis of the reacting tritium-labeled subunits. Comparison of the two-dimensional electrophoretic maps of the immunochemically reacting glycoproteins from liver, kidney, and placenta resulted in the identification of seven placental subunits in common with liver and kidney on the basis of antigenic cross-reactivity, M_r?, and pI. Four placental glycoproteins were not found in the other tissues and are potentially specific to the placenta. Three of the placental subunits were only seen in placenta and kidney. Three of the subunits ran at the dye front and could not be assigned molecular weights. One of the subunits was poorly labeled by tritiation of sialic acid and was not considered.     

Immunohistochemical characterization of purple acid phosphatase-containing leucocytes in the human placenta

Summary A tartrate-resistant acid phosphatase activity was detected in the human placenta. This enzyme displayed immunological properties similar to those of the group of purple acid phosphatases that can be demonstrated with a rabbit polyclonal antibody against bovine spleen purple acid phosphatase. The placental enzyme was mainly localized immunohistochemically to neutrophil granulocytes of the maternal blood between the placental villi and within foetal capillaries using the bovine spleen antibody and the commercial monoclonal antibody M1 directed against an antigen found on mature granulocytes. A minor activity was detected in decidual cells and the syncytiotrophoblast. The presence of purple acid phosphatase in placental granulocytes may be related to special immunological conditions of pregnancy.     

Isolation and characterization of a homogeneous acid phosphatase from catfish liver

A homogeneous, tartrate-inhibitable acid phosphatase (AcPase) was obtained from the liver of channel catfish (Ictalurus punctatus) by the use of Affi Gel-10-coupled aminohexyltartramic acid affinity chromatography. The enzyme has a molecular weight of 82,500 and is a dimer consisting of two apparently equivalent subunits with subunit weights of 35,000 +/- 3000. Amino acid composition data are presented and compared with those of mammalian acid phosphatases. Data suggest that the enzyme is a metalloacid phosphatase. Catfish liver AcPase exhibits two molecular forms with pI 5.66 and 5.37 which were separated by chromatofocusing. A spontaneous conversion of the less acidic form to a more acidic form was observed and this conversion was accompanied by a decreased sensitivity towards tartrate inhibition.     

Histochemical study of a number of hydrolases,including a new acid phosphatase,in various tissues of men and mice

Summary Two acid phosphatases have been demonstrated histochemically in mouse ventral prostate, seminal vesicles, coagulating glands, and liver and in human prostate. The first is the lysosomal acid phosphatase demonstrable by the Gomori technique. The second differs from thisβ-glycerophosphatase in that it splits naphthol AS phosphates but notβ-glycerophosphate; it has a different histochemical pH optimum and it is not inhibited by MoO₄ or NaF. The enzyme does not represent the “tail” of alkaline phosphatase activity as it is not inhibited by inhibitors of alkaline phosphatase and it has a different localization in liver and in human prostate. The enzyme may be membrane-bound but a lysosomal localization has still to be confirmed.     

Developmental expression of murine HPRT. I. Activities,heat stabilities,and electrophoretic mobilities in adult tissues

Total and specific activity of the enzyme hypoxanthine phosphoribosyltransferase (HPRT) varied widely among six tissues from C3H/f mice; the highest levels of activity were in brain. More striking were thermostability differences in tissue enzymes. Although brain, spleen, and kidney HPRT retained 65% basal activity after 15 min at 85 C, heart, liver, and erythrocyte HPRT retained only 20–30% initial activity. Kidney HPRT behaved as monospecific heat-stable enzyme (K _denaturation=0.022/min, and liver enzyme behaved as monospecific heat-labile enzyme (K _denaturation=0.061/min), while other tissues appeared to contain both forms of the enzyme. Multiple electrophoretic activity bands were present in all tissues; no activity band was restricted to a single tissue. The data presented here are consistent with the hypothesis that the distinct tissue properties of HPRT result from posttranslational modification of the product of a single genetic locus which is expressed in all tissues.This study was supported in part by NIH Grant AM 16722 and by an Institutional Biomedical Grant.     

Immunological properties of N-acetyl-β-d-glucosaminidase of normal human liver and of GM2-gangliosidosis liver

Antisera were raised to a partially purified preparation of human liver hexosaminidase and to highly purified preparations of hexosaminidase isoenzymes A and B. All the antisera precipitated the enzyme in an enzymically active form, which could be located on immunodiffusion and immunoelectrophoretic gels by using a histochemical substrate. The antisera to the purified isoenzymes were shown to react with hexosaminidase from human liver, kidney, brain and spleen, but did not cross-react with human liver beta-glucosidase, beta-galactosidase, alpha-mannosidase, beta-xylosidase, arylsulphatase or acid phosphatase. Hexosaminidases A and B were immunologically identical. The immunological properties of the hexosaminidases from livers of patients with three types of GM(2)-gangliosidoses were closely similar. No evidence could be found for cross-reacting material in enzyme-deficient states.     

Cloning, sequence, and developmental expression of a type 5, tartrate-resistant, acid phosphatase of rat bone.

Tartrate-resistant acid phosphatase (TRAP) is a characteristic constituent of osteoclasts and some mononuclear preosteoclasts and, therefore, used as a histochemical and biochemical marker for osteoclasts and bone resorption. We now report the isolation of a 1397-base pair (bp) full-length TRAP/tartrate-resistant acid ATPase (TrATPase) cDNA clone from a neonatal rat calvaria lambda gt11 cDNA library. The cDNA clone consists of a 92-bp untranslated 5'-flank, an open reading frame of 981 bp and a 324-bp untranslated 3'-poly(A)-containing region. The deduced protein sequence of 327 amino acids contains a putative cleavable signal sequence of 21 amino acids. The mature polypeptide of 306 amino acids has a calculated Mr of 34,350 Da and a pI of 9.18, and it contains two potential N-glycosylation sites and the lysosomal targeting sequence DKRFQ. At the protein level, the sequence displays 89-94% homology to TRAP enzymes from human placenta, beef spleen, and uteroferrin and identity to the N terminus of purified rat bone TRAP/TrATPase. An N-terminal amino acid segment is strikingly homologous to the corresponding region in lysosomal and prostatic acid phosphatases. The cDNA recognized a 1.5-kilobase mRNA in long bones and calvaria, and in vitro translation using, as template, mRNA transcribed from the full-length insert yielded an immunoprecipitated product of 34 kDa. In neonatal rats, TRAP/TrATPase mRNA was highly expressed in skeletal tissues, with much lower (less than 10%) levels detected in spleen, thymus, liver, skin, brain, kidney, brain, lung, and heart. In situ hybridization demonstrated specific labeling of osteoclasts at endostal surfaces and bone trabeculae of long bones. Thus, despite the apparent similarity of this osteoclastic TRAP/TrATPase with type 5, tartrate-resistant and purple, acid phosphatases expressed in other mammalian tissues, this gene appears to be preferentially expressed at skeletal sites.     

The relation of the soluble thiamine triphosphatase activity of various rat tissues to nonspecific phosphatases

Polyacrylamide gel electrophoresis was used to investigate the relation of the soluble thiamine triphosphatase activity of various rat tissues to other phosphatases. This technique separated the thiamine triphosphatase of rat brain, heart, kidney, liver, lung, muscle and spleen from alkaline phosphatase (EC 3.1.3.1), acid phosphatase (EC 3.1.3.2) and other nonspecific phosphatase activities. In contrast, the hydrolytic activity for thiamine triphosphate in rat intestine moved identically with alkaline phosphatase in gel electrophoresis. Thiamine triphosphatase from rat liver and brain was also separated from alkaline phosphatase and acid phosphatase by gel chromatography on Sephadex G-100. This gave an apparent molecular weight of about 30,000 and a Stokes radius of 2.5 nanometers for brain and liver thiamine triphosphatase. The intestinal thiamine triphosphatase activity of the rat was eluted from the Sephadex G-100 column as two separate peaks (with apparent molecular weights of over 200,000 and 123,000) which exactly corresponded to the peaks of alkaline phosphatase. The isoelectric point (pI) of the brain thiamine triphosphatase was 4.6 (4 degrees C). The partially purified thiamine triphosphatase from brain and liver was highly specific for thiamine triphosphate. The results suggest that, apart from the intestine, the rat tissues studied contain a specific enzyme, thiamine triphosphatase (EC 3.6.1.28). The specific enzyme is responsible for most of the thiamine triphosphatase activity in these tissues. Rat intestine contains a high thiamine triphosphatase activity but all of it appears to be due to alkaline phosphatase.     

Expression in E. coli and tissue distribution of the human homologue of the mouse Ke 6 gene, 17β-hydroxysteroid dehydrogenase type 8

Expression of the human Ke 6 gene, 17β-hydroxysteroid dehydrogenase type 8, in E. coli and the substrate specificity of the expressed protein were examined. The tissue distribution of mRNA expression of the human Ke 6 gene was also studied using real-time PCR. Human Ke 6 gene was expressed as an enzymatically-active His-tag fusion protein, whose molecular weight was estimated to be 32.5 kDa by SDS-polyacrylamide gel electrophoresis. Expressed human Ke 6 gene effectively catalyzed the conversion of estradiol into estrone. Testosterone, 5α-dihydrotestosterone, and 5-androstene-3β,17β-diol were also catalyzed into the corresponding 17-ketosteroid at 2.4–5.9% that of estradiol oxidation. Furthermore, expressed enzyme catalyzed the reduction of estrone to estradiol, but the rate was a mere 2.3%. Human Ke 6 gene mRNA was expressed in the various tissues examined, such as brain, cerebellum, heart, lung, kidney, liver, small intestine, ovary, testis, adrenals, placenta, prostate, and stomach. Expression of human Ke 6 gene mRNA was especially abundant in prostate, placenta, and kidney. The levels in prostate and placenta were higher than that in kidney, where it is known to be expressed in large quantities.     

Purification and characterization of a ribonuclease from human liver

The major ribonuclease of human liver has been isolated in a four-step procedure. The protein appears homogeneous by several criteria. The amino acid composition and the amino-terminal sequence of the enzyme indicate that the protein is related to human pancreatic ribonuclease and to angiogenin, and that it may be identical with an eosinophil-derived neurotoxin and to a ribonuclease that has been isolated from urine. The catalytic activity of the liver ribonuclease and its sensitivity to iodoacetic acid inactivation also relate the enzyme to the pancreatic RNases, but the liver protein is clearly differentiated by immunological measurements. Antibodies to the liver ribonuclease inhibit its activity, but not that of the human pancreatic enzyme; cross-reactivity in a radioimmunological assay is small but measurable. Immunochemical measurements have been used to examine the distribution of the liver-type protein in other tissues. Inhibition of enzyme activity by anti-liver ribonuclease shows that a cross-reactive enzyme is predominant in extracts of spleen and is a significant component in kidney preparations, while the liver-type protein is almost absent in brain or pancreas homogenates. Cross-reactive ribonuclease is present in serum, but levels are not correlated with any of the disease states examined.     

Glutathione transferase isoenzymes from human prostate.

By using affinity-chromatography and isoelectric-focusing techniques, several forms of glutathione transferase (GSTs) were resolved from human prostate cytosol. All the three major classes of GST, i.e. Alpha, Mu and Pi, are present in human prostate. However, large inter-individual variation in the qualitative and quantitative expression of different isoenzymes resulted in the samples investigated. The most abundant group of prostate isoenzymes showed acid (pI 4.3-4.7) behaviour and were classified as Pi class GSTs on the basis of their immunological and structural properties. Immunohistochemical staining of Pi class GSTs was prevalently distributed in the epithelial cells surrounding the alveolar lumen. Class Mu GSTs are also expressed, although in small amounts and in a limited number of samples, by human prostate. The major cationic isoenzyme purified from prostate, GST-9.6; (pI 9.6; apparent subunit molecular mass of 28 kDa), appears to be different from the cationic GST alpha-epsilon forms isolated from human liver and kidney as evidenced by its structural, kinetical and immunological properties. This enzyme, which accounts for about 20-30% (on protein basis) of total amount of GSTs, is expressed by only 40% of samples. GST-9.6 has the ability to cross-react in immunoblotting analysis with antisera raised against rat liver GST 2-2, rather than with antisera raised against members of human Alpha, Mu and Pi class GSTs. Although prostate GST-9.6 shows close relationship with the human skin GST pI 9.9, it does not correspond to any other known human GST.     

Phosphofructokinase isozymes from human organs and blood cells.

Phosphofructokinase (PFK) isozymes of blood cells and some human tissues were studied by starch gel electrophoresis and immunoprecipitation by anti-muscle and anti-erythrocyte PFK sera. PFK from muscle, heart, brain and placenta were totally precipitated by both antisera. PFK from blood cells (erythrocytes, lymphocytes, granulocytes, platelets) were precipitated more strongly by anti-erythrocyte PFK serum than by anti-muscle PFK serum. Liver, kidney and monoblast PFK were slightly precipitated by both antisera. From the electrophoretic patterns and the immunoprecipitation curves we may conclude that muscle contains the homotetrameric M4 forms; platelet, liver and kidney the homotetrameric E4 form, and blood cells the M-E hybrids. Monoblasts probably contain a E4 type PFK precursor, and heart, placenta and brain, a modified M4 type PFK. Other isozymes, unrelated with muscle and erythrocyte, were revealed in liver and kidney.     

Molecular Cloning and Characterization of a Novel Human C4orf13 Gene, Tentatively a Member of the Sodium Bile Acid Cotransporter Family

By large-scale sequencing analysis of a human fetal brain cDNA library, we isolated a novel human cDNA (C4orf13). This cDNA is 2706 bp in length, encoding a 340-amino-acid polypeptide that contains a typical SBF (sodium bile acid cotransporter family) domain and ten possible transmembrane segments. The putative protein C4orf13 shows high similarity with its orthologs in Mus musculus and Xenopus laevis. Human C4orf13 is mapped to chromosome 4q31.2 and contains 12 exons. RT-PCR analysis shows that human C4orf13 is widely expressed in human tissues, and the expression levels in liver and lung are relatively high, expression levels in placenta, kidney, spleen, and thymus are moderate, low levels of expression are detected in heart, prostate, and testis.The nucleotide sequence reported in this paper has been deposited to GenBank under accession number AY346324.     

A major phosphotyrosyl-protein phosphatase from bovine heart is associated with a low-molecular-weight acid phosphatase

The phosphotyrosyl [Tyr(P)]-immunoglobulin G (IgG) phosphatase activity in the extracts of bovine heart, bovine brain, human kidney, and rabbit liver can be separated by DEAE-cellulose at neutral pH into two fractions. The unbound fraction exhibits a higher activity at acidic than neutral pH while the reverse is true for the bound fraction. Of all tissues examined, the Tyr(P)-IgG phosphatase activity in the unbound fraction measured at pH 5.0 is higher than that in the bound fraction measured at pH 7.2. The acid Tyr(P)-IgG phosphatase activity has been extensively purified from bovine heart. It copurified with an acid phosphatase activity (p-nitrophenyl phosphate (PNPP) as a substrate) throughout the purification procedure. These two activities coelute from various ion-exchange and gel filtration chromatographies and comigrate on polyacrylamide gel electrophoresis, indicating that they reside on the same protein molecule. The phosphatase has a Mr = 15,000 by gel filtration and exhibits an optimum between pH 5.0 and 6.0 when either Tyr(P)-IgG-casein or PNPP is the substrate. It is highly specific for Tyr(P)-protein with little activities toward phosphoseryl [Ser(P)]- or phosphothreonyl [Thr(P)]-protein. The enzyme activities toward Tyr(P)-casein and PNPP are strongly inhibited by microM molybdate and vanadate but insensitive to inhibition by L(+)-tartrate, NaF, or Zn2+. The molecular and catalytic properties of the acid Tyr(P)-protein phosphatase purified from bovine heart are very similar to those of the low-molecular-weight acid phosphatases of Mr = 14,000 previously identified and purified from the cytosolic fraction of human liver, placenta, and other animal tissues.     

Histochemical and immunological demonstration of purple acid phosphatase in human and bovine alveolar macrophages

A tartrate-resistant purple acid phosphatase was localized in human and bovine alveolar macrophages by enzyme- and immuno-histochemistry using an antibody to bovine spleen purple phosphatase. The enzyme could be detected in human and bovine lung tissues as well as on cytospin preparations of alveolar macrophage suspensions from bronchoalveolar lavages. The immunological identity of human and bovine purple phosphatases from alveolar macrophages was demonstrated by Western blot analysis of material separated by polyacrylamide gel electrophoresis. A possible significance of the purple phosphatase as a marker enzyme of activated cells of the mononuclear phagocyte system is discussed.     

Multiple Forms of Phosphatase from Human Brain: Isolation and Partial Characterization of Affi-Gel Blue Nonbinding Phosphatase Activities

Phosphatases extracted from a human brain were resolved into two main groups, namely affi-gel blue-binding phosphatases and affi-gel blue-nonbinding phosphatases. Affi-gel blue binding phosphatases were further separated into four different phosphatase activities, designated P1-P4, and described previously (1). In the present study we describe the affi-gel blue-nonbinding phosphatases which were separated into seven different phosphatase activities, designated P5-P11 by poly-(L-lysine)-agarose and aminohexyl Sepharose 4B chromatographies. These seven phosphatase activities were active toward nonprotein phosphoester. P7-P11 and to some extent P5 could also dephosphorylate a phosphoprotein. They displayed different enzyme kinetics. On the basis of activity peak, the apparent molecular mass as estimated by Sephadex G-200 column chromatography for P5 was 49 kDa; P6, 32 kDa; P7, 150 kDa; P8, 250 kDa; P9, 165 kDa; P10, 90 kDa and P11, 165 kDa. Immunoblot analysis indicated that P8-P11 may belong to PP2B family, whereas P7 may associate with PP2A. The phosphatases P7-P11 were found to be effective in the dephosphorylation of Alzheimer's disease abnormally hyperphosphorylated tau. The resulting dephosphorylated tau regained its activity in promoting the microtubule assembly, suggesting that P7-P11 might regulate the phosphorylation of tau protein in the brain.