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PubMed1985

Phosphotyrosyl-specific protein phosphatase activity of a bovine skeletal acid phosphatase isoenzyme. Comparison with the phosphotyrosyl protein phosphatase activity of skeletal alkaline phosphatase.

A partially purified bovine cortical bone acid phosphatase, which shared similar characteristics with a class of acid phosphatase known as tartrate-resistant acid phosphatase, was found to dephosphorylate phosphotyrosine and phosphotyrosyl proteins, with little activity toward other phosphoamino acids or phosphoseryl histones. The pH optimum was about 5.5 with p-nitrophenyl phosphate as substrate but was about 6.0 with phosphotyrosine and about 7.0 with phosphotyrosyl histones. The apparent Km values for phosphotyrosyl histones (at pH 7.0) and phosphotyrosine (at pH 5.5) were about 300 nM phosphate group and 0.6 mM, respectively, The p-nitrophenyl phosphatase, phosphotyrosine phosphatase, and phosphotyrosyl protein phosphatase activities appear to be a single protein since these activities could not be separated by Sephacryl S-200, CM-Sepharose, or cellulose phosphate chromatographies, he ratio of these activities remained relatively constant throughout the purification procedure, each of these activities exhibited similar thermal stabilities and similar sensitivities to various effectors, and phosphotyrosine and p-nitrophenyl phosphate appeared to be alternative substrates for the acid phosphatase. Skeletal alkaline phosphatase was also capable of dephosphorylating phosphotyrosyl histones at pH 7.0, but the activity of that enzyme was about 20 times greater at pH 9.0 than at pH 7.0. Furthermore, the affinity of skeletal alkaline phosphatase for phosphotyrosyl proteins was low (estimated to be 0.2-0.4 mM), and its protein phosphatase activity was not specific for phosphotyrosyl proteins, since it also dephosphorylated phosphoseryl histones. In summary, these data suggested that skeletal acid phosphatase, rather than skeletal alkaline phosphatase, may act as phosphotyrosyl protein phosphatase under physiologically relevant conditions.

4-Nitrophenylphosphatase↗
PubMed1989

Carbohydrate removal fails to eliminate the heterogeneity of human prostatic acid phosphatase.

Human prostatic acid phosphatase is known to display considerable charge heterogeneity upon isoelectric focusing. The structural basis of this heterogeneity is not known, although it has been widely attributed to variations in the nature of the carbohydrate chains or to substituents on the carbohydrate chains of the glycoprotein. In this study, the role of the carbohydrate chains in the charge heterogeneity of the protein was examined. First, sialic acid residues were removed by treatment of the acid phosphatase with neuraminidase. The desialo enzyme was fractionated and purified by L-tartramic acid affinity chromatography. Then, after the protein oligosaccharide linkages were made accessible by the presence of NP-40 or by denaturing the protein, the protein was completely deglycosylated by endo-beta-N-acetylglucosaminidase F at pH 4.5 and 9.3. Two discrete intermediates were clearly resolved by SDS gel electrophoresis during the deglycosylation of the denatured protein at pH 9.3, indicating the existence of three sites of glycosylation on the protein. Peptide mixtures were obtained by digestion of carboxymethylated and citraconylated derivatives of the enzyme with trypsin and the glycopeptides were isolated. The amino acid compositions of the glycopeptides were consistent with the interpretation that there are a minimum of two sites of glycosylation on each peptide subunit of the enzyme. Isoelectric focusing experiments on the native, desialo, and denatured, deglycoso acid phosphatase showed that the heterogeneity of the protein is not eliminated either by desialylation or by deglycosylation. Thus, the electrophoretic heterogeneity of human prostatic acid phosphatase does not lie primarily in the oligosaccharide part of the glycoprotein or in altered conformational states of the protein, but in structural variations of the polypeptide itself. The heterogeneity may be due to variations at the C-terminus, partial deamidation, phosphorylation, sulfation or other posttranslational modifications of the protein chain.

Acetylglucosamine↗
PubMed1992

Acid phosphatases in mammalian tissues. Evidence for the existence of a 57 kDa Zn(2+)-dependent acid phosphatase form.

1. A comparative study of multiple forms of acid phosphatase (AcPase) in various organs of mammals was carried out. 2. These studies indicated that the high-molecular weight AcPase is preferentially expressed by tissues which undergo cell proliferation such as epithelial tissues; on the contrary, the low-molecular weight enzyme seems to be characteristic of highly differentiated tissues such as nervous, muscle and blood erythrocytes. 3. The existence of a new AcPase activated by Zn2+ ions was observed in all tissues studied with the exception of erythrocytes. 4. The enzyme shows a molecular weight of 57 kDa, is insensitive to NaF, hydrolyzes p-nitro-phenylphosphate and o-c-phenylphosphate; ATP, a-naphthyl-phosphate and beta-glycerolphosphate are also dephosphorylated.

Acid Phosphatase↗
PubMed1996

Phosphatase inhibitors--III. Benzylaminophosphonic acids as potent inhibitors of human prostatic acid phosphatase.

Further investigation of the structural requirements of a series of benzylphosphonic acid inhibitors of human prostatic acid phosphatase has led to the highly potent series of alpha-aminobenzylphosphonic acids. The alpha-benzylaminobenzylphosphonic acid, with an IC50 = 4 nM, exhibited a 3500-fold improvement in potency over the carbon analogue, alpha-phenylethyl. The enhanced potency may be due to a combination of four favorable interactions including those with the phosphate binding region, the presence the hydrophobic moieties of the benzylamino and phenylphosphonic acid, and a rigid conformer produced by an internal salt bridge between the phosphonate and the alpha-amino group. Replacement of the phosphonic acid moiety with a phosphinic or carboxylic acid as well as deletion of the benzyl substitution of the alpha-amino group led to great reductions in potency.

Acid Phosphatase↗
PubMed1970

Control of ribonuclease and acid phosphatase by auxin and abscisic acid during senescence of Rhoeo leaf sections.

We report the effects of abscisic acid and auxin (alpha-naphthalene acetic acid) on regulation of enzyme synthesis during senescence of leaf sections of Rhoeo discolor Hance. Abscisic acid always accelerates the onset of and enhances the magnitude of the increase in activity of acid phosphatase; this is followed by an acceleration of the onset of a rapid increase in free space.RNase activity increases 2- to 5-fold after cutting of leaf sections. Abscisic acid increases RNase activity and inhibits the rate of incorporation of uridine and leucine in leaf sections removed from plants grown under stress but not favorable conditions. Auxin inhibits the increase in RNase and acid phosphatase and suppresses the effects of abscisic acid. The increase in activity of RNase and acid phosphatase is inhibited by inhibitors of RNA and protein synthesis. This and other evidence suggests that the increases in hydrolase activity could result from new enzyme synthesis. The possible significance of the results in respect of hormonal regulation of enzyme activity and senescence is discussed.

Acid Phosphatase↗
PubMed1988

Acid phosphatase as a selective marker for a class of small sensory ganglion cells in several mammals: spinal cord distribution, histochemical properties, and relation to fluoride-resistant acid phosphatase (FRAP) of rodents.

Fluoride-resistant acid phosphatase (FRAP) activity as characterized in rat and mouse was studied in sensory ganglion and spinal cord of several mammals, using both the Gomori lead-ion capture and azo-dye coupling methods. FRAP was specifically localized to small- and medium-diameter primary afferent neurons and inner substantia gelatinosa of all nonrodent animals studied, including rabbit, cat, dog, monkey, cow, and human. In rabbit, sciatic nerve transection resulted in depletion of enzymatic activity in ipsilateral spinal cord dorsal horn in a pattern corresponding to the distribution of central terminals of the nerve. Further analysis of the substrate specificity and pH dependence of FRAP was carried out primarily in rat sensory ganglion and spinal cord; the enzyme was found to hydrolyze a wide variety of phosphomonoesters in a relatively nonselective manner at both pH 5 and pH 7, including 5'-nucleotides, phosphorylated amino acids, and several exogenous compounds. The visualization of FRAP-like activity in several nonrodent species is discussed with reference to previous work indicating its presence only in mouse and rat. Technical factors are considered that limit the applicability of the lead-ion histochemical method in demonstration of FRAP and in efforts at functional characterization of the enzyme, especially in light of its ability to hydrolyze a broad spectrum of substrates over a wide pH range. Alternative interpretations of the expression of acid phosphatase activity in a select class of small sensory ganglion cells are suggested, including several possible non-synaptic roles of FRAP in the peripheral nervous system.

Acid Phosphatase↗
PubMed1987

Serum osteocalcin, bone alkaline phosphatase isoenzyme and plasma tartrate resistant acid phosphatase in patients on chronic maintenance hemodialysis.

Biochemical indices of bone formation (serum osteocalcin and bone alkaline phosphatase isoenzyme) and osteoclastic function (plasma tartrate resistant acid phosphatase) were measured in 43 patients undergoing chronic hemodialysis and in 27 patients with primary hyperparathyroidism. The mean values for bone alkaline phosphatase isoenzyme and plasma tartrate resistant acid phosphatase but not for osteocalcin were significantly higher in primary hyperparathyroidism as compared with dialyzed patients. A significant positive correlation was found between the biochemical indices of osteoblasts and osteoclasts both in primary hyperparathyroidism and in dialyzed patients, indicating biological coupling between bone resorption and formation under these conditions. The regressions of osteocalcin vs bone alkaline phosphatase isoenzyme and/or plasma tartrate resistant acid phosphatase in dialyzed patients paralleled those in primary hyperparathyroidism but their distance differed significantly. It is concluded that in patients with renal failure, an increase in circulating osteocalcin by a relatively constant portion reflects decreased renal clearance. Any additional increase in osteocalcin serum level indicates an increased skeletal production of osteocalcin. The clinical value of bone alkaline phosphatase isoenzyme and plasma tartrate resistant acid phosphatase appears to be comparable with that of serum osteocalcin in primary hyperparathyroidism, and more exact than osteocalcin in renal failure.

Acid Phosphatase↗
PubMed1998

Studies on the protein tyrosine phosphatase activity of tartrate-resistant acid phosphatase.

Tartrate-resistant acid phosphatase (TRAP) is an enzyme with unknown biological function. In human tissues, its expression is restricted to bone-resorbing osteoclasts and activated macrophages. Osteoclasts secrete TRAP to the circulation during bone resorption. Reduction of the enzyme's binuclear iron center is important in regulating its activity. The purple form of the enzyme is inactive and contains two ferric ions. Mild reduction activates it to a pink form containing one ferric and one ferrous ion. Instead, strong reduction removes the iron content, resulting in a colorless, inactive enzyme. We describe spontaneous activation of the purple form to the pink form upon incubation at +37 degrees C. Further incubation results in slow inactivation of the enzyme and color change to yellowish. The enzyme purified from osteoclasts is a mixture of the purple and pink forms, but the enzyme purified from serum represents the yellowish form. We suggest that the newly synthesized enzyme is purple and reduced in the cell to the functionally active pink form. After fulfilling its biological function in the cell, the enzyme is further reduced to the yellowish form and secreted into the circulation. In the serum, further reduction would dissociate the iron content. The enzymes from osteoclasts and macrophages had similar catalytic properties, both being active as a protein tyrosine phosphatase (PTPase). The acid phosphatase (AcP) and PTPase activities were similar, and the preferred AcP substrate, pNPP, was processed in the same active site as phosphotyrosine. Our results suggest that redox-regulated PTPase activity may be a major function of TRAP in vivo.

Acid Phosphatase↗
PubMed1978

Alkaline phosphatase and tartrate resistant acid phosphatase activity in cells of prolymphocytic leukemia.

In a typical case of prolymphocytic leukemia, blood smears and lymph node imprints have been investigated cytologically and cytochemically. It could be shown that many leukemic cells in both blood smears and lymph node imprints contained tartrate resistant acid phosphatase activity. Furthermore, the lymph node imprints disclosed many cells with a positive alkaline phosphatase reaction. Such a reaction hitherto has not been described in malignant cells of lymphoproliferative diseases. The cytochemical results underline that prolymphocytic leukemia indeed is a separate entity which can be differentiated from hairy cell leukemia and chronic lymphatic leukemia not only morphologically but also cytochemically. In addition, the case shows that leukemic blood cells are not inevitably identical with those occurring in organ infiltrates.

Acid Phosphatase↗