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PubMed2006

Regulatory role of polyamine in the acid phosphatase from potato tubers.

Effects of polyamine and metal ions on the new type of acid phosphatase purified from potato (Solanum tuberosum L. Irish Cobbler) tubers were analyzed. The enzyme belongs to nonspecific acid phosphatase family (EC 3.1.3.2), which hydrolyzes various phosphorylated substrates. The enzyme hydrolyzed inorganic pyrophosphate as a preferred substrate, and exhibited the hyperbolic kinetics with respect to the substrate, inorganic pyrophosphate in the absence of metal cations. Polyamine activated the enzyme effectively by lowering the K(m) value without appreciable changes in the maximal velocity. The most effective polyamines as activators were spermine and spermidine. Mg(2+) ion increased the K(m) value without affecting the maximal velocity of the enzyme, but Ca(2+) ion decreased both the K(m) and V(max) values. Increasing concentrations of spermine also decreased the K(m) value irrespective of Mg(2+) ion included, but gave a constant K(m) and V(max) values in the absence and presence of Ca(2+) ion. Action of spermine and metal ions can be explained by the complex formation with the substrate pyrophosphate. The acid phosphatase from potato can utilize the pyrophosphate-spermine or pyrophosphate-Ca(2+) complex as the preferred substrates. However, the enzyme can use the pyrophosphate-Mg complex with a weak affinity for the active site. Polyamine activates acid phosphatase in the absence and presence of metal cations, and activation by polyamine of the enzyme may contribute to the stimulation of starch biosynthesis and the control of glycolysis/gluconeogenesis by regulating PPi levels in growing potato tubers.

Acid Phosphatase↗
PubMed1990

Serum acid phosphatase in patients with localised prostatic cancer, benign prostatic hyperplasia or normal prostates.

Serum acid phosphatase levels were determined in 247 men with surgically confirmed intracapsular prostatic cancer (30 patients), benign prostatic hyperplasia (BPH) (114 patients) or palpably normal prostates (103 men). Both radioimmunoassay (245 cases) and an enzymatic method (218 cases) were used. Using radioimmunoassay, the mean serum prostatic acid phosphatase (PAP) level was significantly higher in patients with BPH than in patients with intracapsular cancer or men with normal prostates. The weight of hyperplastic tissue removed during operation in the BPH group correlated closely with PAP concentrations. Age or the presence (or absence) of an indwelling catheter had no effect on PAP concentration. Using the enzymatic method, the highest levels of acid phosphatase were also detected in patients with BPH but the difference was less marked. It was concluded that intracapsular cancer does not elevate serum acid phosphatase levels as determined by radioimmunoassay or an enzymatic method. BPH alone leads to significant rises in PAP concentrations. The degree of BPH correlates with PAP levels.

Acid Phosphatase↗
PubMed1981

Comparison of the tartrate-resistant acid phosphatase in Gaucher's disease and leukemic reticuloendotheliosis.

Tartrate-resistant acid phosphatase was isolated from serum and spleen of patients affected by Gaucher's disease. Electrophoretic and antigenic properties were compared to the enzyme isolated from hairy cells described in a previous study (9). The enzyme isolated from Gaucher serum has electrophoretic and antigenic properties identical to the acid phosphatase band 5b of hairy cells. The major tartrate-resistant acid phosphatase in the Gaucher spleen is band 5a. Bands 5a and 5b have identical protein structure indicated by their identical antigenicity. The removal of carbohydrate from band 5a by sialidase converted band 5a to 5b.

Acid Phosphatase↗
PubMed1999

Estimation of PC12 cell numbers with acid phosphatase assay and mitochondrial dehydrogenase assay: dopamine interferes with assay based on tetrazolium.

Both the acid-phosphatase and mitochondrial dehydrogenase assay have been used to quantify cell numbers. The commonly used acid-phosphatase assay uses p-nitrophenyl phosphate as a substrate, while the mitochondrial dehydrogenase assay is based on the conversion of tetrazolium to formazan. Our experimental results showed that the former assay was more sensitive in detecting small numbers of PC12 cells (200-10,000 cells/well), whereas the latter was useful for larger numbers of cells (2000-40,000 cells/well). The number of PC12 cells decreased after dopamine treatment, according to the acid-phosphatase assay and by direct cell counts under a light microscope. However, the optical densities measured by the mitochondrial dehydrogenase assay increased after dopamine treatment. We tried to clarify discrepancies between the two assays, since dopamine is an important neurotransmitter and both assays are commonly used to estimate cell numbers. To elucidate the interference between dopamine and tetrazolium salt, cell-free control experiments were performed. Dopamine and other catecholamines (adrenaline and noradrenaline) reacted with tetrazolium and, thus, produced a false positive reaction in the assay. We therefore conclude that the tetrazolium assay is not a suitable method for evaluating the number of catecholamine-treated cells, while the acid-phosphatase assay is reliable and sensitive.

Acid Phosphatase↗
PubMed1982

Brain phagocytes: source of high acid phosphatase activity.

A stab wound was produced in the adult rat cerebral cortex, and the progress of enzyme cytochemistry of phagocytosis was studied over 450 days. Light- and electron-microscopic observations were made to establish the origin of high acid phosphatase activity commonly seen at the site of brain lesions. Cells with phagocytic potential became differentiated and activated by the presence of degenerating neurons. The Golgi-lysosomal system of the phagocytes became elaborated, as evidenced by thiamine pyrophosphatase and acid phosphatase activities, the synthesis of acid phosphatase was increased, and the enzyme then secreted into the digestive vacuoles containing dead cells to be digested. Progress of the digestive process resulted in the accumulation of large amounts of acid phosphatase reaction product within the digestive vacuoles. The results showed that the phagocytes were the only detectable source of increased acid phosphatase activity at the site of injury in the cerebral cortex. In contrast to the phagocytes, newly formed multi-nucleated giant cells exhibited weak acid phosphatase, and intense cytochrome oxidase activities, the difference between the two cells reflecting the functional characteristics of each.

Acid Phosphatase↗
PubMed2002

Bromoperoxidase activity of vanadate-substituted acid phosphatases from Shigella flexneri and Salmonella enterica ser. typhimurium.

Vanadium haloperoxidases and the bacterial class A nonspecific acid phosphatases have a conserved active site. It is shown that vanadate-substituted recombinant acid phosphatase from Shigella flexneri (PhoN-Sf) and Salmonella enterica ser. typhimurium (PhoN-Se) in the presence of H2O2 are able to oxidize bromide to hypobromous acid. Vanadate is essential for this activity. The kinetic parameters for the artificial bromoperoxidases have been determined. The Km value for H2O2 is about the same as that for the vanadium bromoperoxidases from the seaweed Ascophyllum nodosum. However, the Km value for Br- is about 10-20 times higher, and the turnover values of about 3.4 min-1 and 33 min-1 for PhoN-Sf and PhoN-Se, respectively, are much slower, than those of the native bromoperoxidase. Thus, despite the striking similarity in the active-site structures of the vanadium haloperoxidases and the acid phosphatase, the turnover frequency is low, and clearly the active site of acid phosphatases is not optimized for haloperoxidase activity. Like the native vanadium bromoperoxidase, the vanadate-substituted PhoN-Sf and PhoN-Se catalyse the enantioselective sulfoxidation of thioanisole.

Acid Phosphatase↗
PubMed1982

Monoclonal anti-human prostatic acid phosphatase antibodies.

Hybrid cell lines producing monoclonal antibodies against human prostatic acid phosphatase (E. C. 3.1.3.2) were prepared by the fusion of mouse myeloma cells with the spleen cells of BALB/c mice and Lewis rats immunized with prostatic acid phosphatase (PAP). Approximately 14% of the hybrid cell microcultures which produced specific antibodies were cloned, and 6 eventually yielded stable cell lines. The monoclonal antibodies produced by these 6 hybridomas were characterized for their isotypes, isoelectric points, concentrations and affinities. The specificity of these monoclonal antibodies was further investigated by radioimmunoassay and immunohistochemical methods. All of the 6 monoclonal antibodies exhibited strict specificity for prostatic acid phosphatase.

Acid Phosphatase↗
PubMed1999

A type 5 acid phosphatase gene from Arabidopsis thaliana is induced by phosphate starvation and by some other types of phosphate mobilising/oxidative stress conditions.

Low phosphorous availability, a common condition of many soils, is known to stimulate phosphatase activity in plants; however, the molecular details of this response remain mostly unknown. We purified and sequenced the N-terminal region of a phosphate starvation induced acid phosphatase (AtACP5) from Arabidopsis thaliana, and cloned its cDNA and the corresponding genomic DNA. The nucleotide sequence of the cDNA predicted that AtACP5 is synthesised as a 338 amino acid-long precursor with a signal peptide. AtACP5 was found to be related to known purple acid phosphatases, especially to mammal type 5 acid phosphatases. Other similarities with purple acid phosphatases, which contain a dinuclear metal centre, include the conservation of all residues involved in metal ligand binding and resistance to tartrate inhibition. In addition, AtACP5, like other type 5 acid phosphatases, displayed peroxidation activity. Northern hybridisation experiments, as well as in situ glucuronidase (GUS) activity assays on transgenic plants harbouring AtACP5:GUS translational fusions, showed that AtACP5 is not only responsive to phosphate starvation but also to ABA and salt stress. It is also expressed in senescent leaves and during oxidative stress induced by H2O2, but not by paraquat or salicylic acid. Given its bifunctionality, as it displays both phosphatase and peroxidation activity, we propose that AtACP5 could be involved in phosphate mobilisation and in the metabolism of reactive oxygen species in stressed or senescent parts of the plant.

Acid Phosphatase↗
PubMed2004

Structural and kinetic properties of a novel purple acid phosphatase from phosphate-starved tomato (Lycopersicon esculentum) cell cultures.

An intracellular acid phosphatase (IAP) from P(i)-starved (-P(i)) tomato ( Lycopersicon esculentum ) suspension cells has been purified to homogeneity. IAP is a purple acid phosphatase (PAP), as the purified protein was violet in colour (lambda(max)=546 nm) and was insensitive to L-tartrate. PAGE, periodic acid-Schiff staining and peptide mapping demonstrated that the enzyme exists as a 142 kDa heterodimer composed of an equivalent ratio of glycosylated and structurally dissimilar 63 (alpha-subunit) and 57 kDa (beta-subunit) polypeptides. However, the nine N-terminal amino acids of the alpha- and beta-subunits were identical, exhibiting similarity to the deduced N-terminal portions of several putative plant PAPs. Quantification of immunoblots probed with rabbit anti-(tomato acid phosphatase) immune serum revealed that the 4-fold increase in IAP activity due to P(i)-deprivation was correlated with similar increases in the amount of antigenic IAP alpha- and beta-subunits. IAP displayed optimal activity at pH 5.1, was activated 150% by 10 mM Mg(2+), but was potently inhibited by Zn(2+), Cu(2+), Fe(3+), molybdate, vanadate, fluoride and P(i). Although IAP demonstrated broad substrate selectivity, its specificity constant ( V (max)/ K (m)) with phosphoenolpyruvate was >250% greater than that obtained with any other substrate. IAP exhibited significant peroxidase activity, which was optimal at pH 9.0 and insensitive to Mg(2+) or molybdate. This IAP is proposed to scavenge P(i) from intracellular phosphate esters in -P(i) tomato. A possible secondary IAP role in the metabolism of reactive oxygen species is discussed. IAP properties are compared with those of two extracellular PAP isoenzymes that are secreted into the medium of -P(i) tomato cells [Bozzo, Raghothama and Plaxton (2002) Eur. J. Biochem. 269, 6278-6286].

Acid Phosphatase↗
PubMed1986

The human red cell acid phosphatase is a phosphotyrosine protein phosphatase which dephosphorylates the membrane protein band 3.

Human red cell cytosol acid phosphatase activity is supported by a main enzyme which can be extracted by DEAE and phosphocellulose chromatography. It uses pNPP as a substrate and is a protein phosphatase specific to phosphotyrosine. It dephosphorylates the tyrosine-phosphorylated cytosolic fragment of membrane protein 3. When taken together, these results suggest that the physiological role of red cell acid phosphatase is the FB3 phosphotyrosine dephosphorylation. Whatever it may be phosphotyrosine protein phosphatase activity is the first role of red cell acid phosphatase to be demonstrated.

Acid Phosphatase↗
PubMed1992

Overexpression, site-directed mutagenesis, and mechanism of Escherichia coli acid phosphatase.

Site-directed mutagenesis was used to examine the catalytic importance of 2 histidine and 4 arginine residues in Escherichia coli periplasmic acid phosphatase (EcAP). The residues that were selected as targets for mutagenesis were those that were also conserved in a number of high molecular weight acid phosphatases from eukaryotic organisms, including human prostatic and lysosomal acid phosphatases. Both wild type EcAP and mutant proteins were overproduced in E. coli using an expression system based on the T7 RNA polymerase promoter, and the proteins were purified to homogeneity. Examination of the purified mutant proteins by circular dichroism and proton NMR spectroscopy revealed no significant conformational changes. The replacement of Arg16 and His17 residues that were localized in a conserved N-terminal RHGXRXP motif resulted in the complete elimination of EcAP enzymatic activity. Critical roles for Arg20, Arg92, and His303 were also established because the corresponding mutant proteins exhibited residual activities that were not higher than 0.4% of that of wild type enzyme. In contrast, the replacement of Arg63 did not cause a significant alteration of the kinetic parameters. The results are in agreement with a previously postulated distant relationship between acid phosphatases, phosphoglycerate mutases, and fructose-2,6-bisphosphatase. These and earlier results are also consistent with the conclusion that 2 histidine residues participate in the catalytic mechanism of acid phosphatases, with His17 playing the role of a nucleophilic acceptor of the phospho group, whereas His303 may act as a proton donor to the alcohol or phenol.

Acid Phosphatase↗
PubMed1990

Lysosomal acid phosphatase is transported via endosomes to lysosomes.

Involvement of endosomes in transport of newly synthesized acid phosphatase to lysosomes was investigated using the Golgi fraction (GF1 + 2), enriched in endosomes. The Golgi fraction (GF1 + 2) was prepared from the livers of rats given [35S]methionine and asialofetuin conjugated-horseradish peroxidase (HRP). Newly synthesized acid phosphatase in the endosomes containing internalized asialofetuin-HRP was measured as a loss of the detectable labeled enzyme after 3,3'-diaminobenzidine (DAB) and H2O2 reaction, due to formation of insoluble polymers which reduce protein antigenicity. With this procedure, acid phosphatase was all but undetectable in the Golgi fraction. Thus, newly synthesized acid phosphatase is apparently transported to lysosomes by endosomes.

Acid Phosphatase↗
PubMed1981

A clinical assay for prostatic acid phosphatase using choline phosphate as a substrate: comparison with thymolphthalein phosphate.

We describe an assay method using choline O-phosphate as a substrate for the measurement of serum prostatic acid phosphatase as an aid in the diagnosis of prostatic cancer. Choline phosphate is hydrolyzed by homogeneous prostatic acid phosphatase, and it is also hydrolyzed by an acid phosphatase present in the serum of prostatic carcinoma patients. In contrast, serum samples from apparently healthy persons do not exhibit any significant choline O-phosphate phosphatase activity. There is a correlation of 98% (n = 46) between choline O-phosphate phosphatase activity and typical measurement for prostatic acid phosphatase activity carried out using thymolphthalein monophosphate as the substrate. The new method appears to be as accurate as colorimetric methods based on thymolphthalein phosphate as a substrate. Although not as sensitive as immunologically based methods, the present technique for measuring prostatic acid phosphatase activity using choline phosphate as a substrate is economical and relatively simple.

Acid Phosphatase↗
PubMed1978

Bone marrow acid phosphatase in staging of prostatic cancer: how reliable is it?

To evaluate the reliability of bone marrow acid phosphatase in the staging of prostatic carcinoma we analyzed 50 bone marrow samples collected at random from the hematology service at this hospital. The samples were assayed for acid phosphatase content by a colorimetric method using sodium thymolphthalein monophosphate as a substrate and by 2 immunochemical assays developed at our laboratory (counter immunoelectrophoresis and radioimmunoassay). We found a high percentage (61 per cent) of falsely positive results in patients with various hematological diseases without evidence of prostatic carcinoma by the colorimetric evaluation. All of these patients except 1 had negative immunochemical assay. Until a specific assay for prostatic acid phosphatase is developed for clinical use we caution the use of a single elevation of bone marrow acid phosphatase as a parameter of metastatic disease.

Acid Phosphatase↗
PubMed1989

Apparent lack of effect of obesity on the soluble phosphatidic acid phosphatase activity in human adipose tissue.

In view of previous reports that the activity of the Mg(++)-dependent phosphatidic acid phosphatase in adipose tissues of rat and mouse is elevated in obesity, we attempted to assay this activity in biopsies of human omental adipose tissue obtained from normal-weight and morbidly obese subjects in connection with operations. The major portion of the phosphatidic acid phosphatase activity was found in the cytosol, and the small amount found in the microsomal fraction was too low for accurate measurement. It was not possible to assay the activity in the crude cytosol. After precipitation with ammonium sulfate, however, the enzyme activity was linear with both the incubation time and the concentration of enzyme. It was not possible to obtain substrate saturation of the enzyme under the conditions employed. When assayed in the presence of a high concentration of substrate (0.6 mmol/l) the activity obtained in normal-weight patients, 7.8 +/- 2.4 nmol/mg protein/min (n = 10), was not significantly different from that in morbidly obese patients, 5.6 +/- 0.8 nmol/mg protein/min (n = 10). There was no relation between the size of adipose cells and phosphatidic acid phosphatase activity. Furthermore, there was no apparent relation between phosphatidic acid phosphatase activity in omental adipose tissue and that in the liver. The findings suggest that the increased biosynthesis of triglycerides in human obesity is not associated with an increased capacity of the soluble phosphatidic acid phosphatase in adipose tissue.

Adipose Tissue↗
PubMed2001

Persistence of spermatozoa and prostatic acid phosphatase in specimens from deceased individuals during varied postmortem intervals.

The survival of spermatozoa and the persistence of prostatic acid phosphatase has been an area of interest for investigators of sexual assault. However, not much documentation exists concerning the examination of a deceased individual with regard to the postmortem interval and presence of such evidence. The authors reviewed cases referred to the medical examiner's office during a 10-year period. During this time, 199 cases were both autopsied and examined for sexual assault. In particular, these examinations included procurement of swabs for Papanicolaou staining of smears and for quantitation of prostatic acid phosphatase. Most of the victims were female, although a few were male. In the majority of cases, the swabs for smears and prostatic acid phosphatase were taken from oral, vaginal, and anorectal areas in females and oral and anorectal areas in males. The smears all were stained with the routine Papanicolaou stain, and intact spermatozoa and spermatozoan heads were sought. The prostatic acid phosphatase was analyzed by the microparticle enzyme immunoassay method and reported as ng/ml. A level of greater than 100 ng/ml was considered positive. The cases were analyzed with respect to postmortem interval; presence or absence of intact spermatozoa or spermatozoan heads; presence of an elevated prostatic acid phosphatase; body location of the specimen; the time of year; location of the victim; and physical injury (anogenital) of sexual assault. The authors hope that by examining the laboratory evidence of sexual assault, a correlation can be drawn between the presence or absence of such evidence and the aforementioned variables.

Acid Phosphatase↗
PubMed1986

Subcellular localization of high- and low-molecular weight acid phosphatases from chicken liver.

The subcellular localization of high and low molecular weight acid phosphatases in chicken liver was studied. The high molecular weight acid phosphatase is mainly associated with the particulate fraction, particularly with the mitochondrial-lysosomal fraction, whereas the low molecular weight form seems to be a soluble cytoplasmic enzyme. Biochemical properties including optimal pH, molecular weight determination and the effect of some modifier substances indicate that mitochondria-lysosomes and microsomes contain the same high molecular weight acid phosphatase form.

Acid Phosphatase↗
PubMed1989

Changes in acid phosphatase activity in rat liver after ischemia.

The effect of ischemia on the stability, i.e. the permeability of the lysosomal membrane of rat liver has been studied using quantitative histochemical analysis of acid phosphatase activity. Ischemia in vitro was performed for 0-240 min at 37 degrees C and ischemia in vivo for 60 min was followed by 1, 5, 24 and 48 h of reperfusion. Acid phosphatase activity was demonstrated in cryostat sections using naphthol AS-BI phosphoric acid as substrate and polyvinyl alcohol was added to the incubation medium to counteract diffusion phenomena. Ischemia in vitro up to 240 min did not affect the localization nor the total activity of acid phosphatase activity. After 60-min ischemia in vivo followed by 1-h reperfusion distinct areas showed decreased acid phosphatase activity. A further decrease in activity was observed after 5 h reperfusion. Final reaction product generated by acid phosphatase activity was rather diffusely distributed in border zones between normal and damaged tissue after 24 and 48 h of reperfusion following 60 min ischemia in vivo. It is concluded that not ischemia itself but rather reperfusion affects the stability of the lysosomal membrane due to the occurrence of oxygen-derived free radicals and/or imbalanced Ca2+ concentration. Restoration of the blood flow causes leakage of acid phosphatase from the lysosomes into the cytoplasm of liver parenchymal cells and from there to the blood.

Acid Phosphatase↗