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PubMed1989

Influence of glycosylation on the oligomeric structure of yeast acid phosphatase.

Secreted yeast acid phosphatase is found to be an octamer under physiological conditions rather than a dimer, as previously believed. The octameric form of the enzyme dissociates rapidly into dimers at pH below 3 and above 5, or by treatment with guanidine hydrochloride or urea, without further dissociation of dimers. Crosslinking experiments revealed that the dissociation of the octamer occurs through very unstable hexamers and tetramers, showing that the octamer is built of dimeric units. Dissociation to dimer was in all cases accompanied with a loss of most of the enzyme activity. The underglycosylated acid phosphatase, with less than eight carbohydrate chains per subunit, secreted from cells treated with moderate tunicamycin concentrations, contained besides octamers a high proportion of the dimers. With decreasing levels of enzyme glycosylation, the proportion of dimers increases and the amount of octamers correspondingly decreases. Furthermore, underglycosylated octamers were found to be significantly less stable than the fully glycosylated ones. This showed that carbohydrate chains play a significant role in the octamer formation in vivo, and in stabilization of the enzyme octameric form.

Acid Phosphatase↗
PubMed2001

Changes in mRNA levels of alkaline phosphatase and tartrate-resistant acid phosphatase in femur of ovariectomized rats: effects of estrogen and unloading.

Our previous studies demonstrated that estrogen (E2) prevents the development of disuse atrophy of the femur in tail-suspended rats. To elucidate the mechanisms of this E2 action, we investigated the effects of E2 on the expression of alkaline phosphatase (ALP, a marker for bone formation) and tartrate-resistant acid phosphatase (TRAP, a marker for bone resorption) in the femur of ovariectomized and tail-suspended rats. One group of ovariectomized rats received estradiol dipropionate (OVX-E2), and the other the vehicle alone (OVX). Each group was subjected to tail-suspension. After 1, 3, 5 or 7 days of suspension, ALP and TRAP mRNA levels were determined by Northern blot analysis. The ALP mRNA level was not altered by suspension in the OVX group, but it gradually increased in the OVX-E2 group, the highest level being observed at day 5 of suspension. In contrast, TRAP mRNA significantly increased at days 5 and 7 in the OVX group, while it is decreased significantly from day 3 to 7 in the OVX-E2 group. These results indicate that E2 prevents disuse atrophy of the femur in an ovariectomized and tail-suspended rat model by stimulating bone formation and by inhibiting bone resorption.

Acid Phosphatase↗
PubMed1988

Phosphotyrosine phosphatase activity of human and canine acid phosphatases of prostatic origin.

Human and canine prostatic specimens containing high levels of acid phosphatase (AP) activity were tested, at acid pH, for their ability to hydrolyze the major phosphoaminoacids present in phosphorylated proteins, phosphoserine (p-ser), phosphothreonine (p-thr), and phosphotyrosine (p-tyr). The cleavage of a synthetic substrate, para-nitrophenyl-phosphate (p-npp), was also measured as an indicator of AP activity; its inhibition by sodium-L-tartrate (T) was used as a criterion to identify prostatic acid phosphatase (PAP). It was found that: 1) the Km of p-tyr and p-npp were 2.0 mM and 0.41 mM, respectively, with similar Vmax values (0.078 and 0.087 mumoles of phosphate (Pi) liberated per minute per milligram of protein); 2) the ID50 were 0.25 mM and 0.50 mM with sodium orthovanadate (VO4) and T, respectively, using p-npp as substrate-with p-tyr as substrate, the values obtained were 0.016 mM and 0.11 mM, respectively; 3) activity toward p-ser and p-thr was minimal; 4) native PAP from dog seminal plasma, with a molecular weight of 90-100 kD, as determined by gel filtration on HPLC, hydrolyzed p-tyr preferentially, and this phosphatase (Pase) activity was also strongly inhibited by both T and VO4; and 5) the AP present in human and canine prostatic tissue and cells, as well as in their secretions, also preferentially hydrolyzed phosphotyrosine, and it was inhibited by T and VO4. It is proposed that these p-tyr Pases may be involved in the local regulation of prostatic growth.

Acid Phosphatase↗
PubMed1999

Crystal structure of mammalian purple acid phosphatase.

BACKGROUND: Mammalian purple acid phosphatases are highly conserved binuclear metal-containing enzymes produced by osteoclasts, the cells that resorb bone. The enzyme is a target for drug design because there is strong evidence that it is involved in bone resorption. RESULTS: The 1.55 A resolution structure of pig purple acid phosphatase has been solved by multiple isomorphous replacement. The enzyme comprises two sandwiched beta sheets flanked by alpha-helical segments. The molecule shows internal symmetry, with the metal ions bound at the interface between the two halves. CONCLUSIONS: Despite less than 15% sequence identity, the protein fold resembles that of the catalytic domain of plant purple acid phosphatase and some serine/threonine protein phosphatases. The active-site regions of the mammalian and plant purple acid phosphatases differ significantly, however. The internal symmetry suggests that the binuclear centre evolved as a result of the combination of mononuclear ancestors. The structure of the mammalian enzyme provides a basis for antiosteoporotic drug design.

Acid Phosphatase↗
PubMed1996

Characterization and sequencing of a respiratory burst-inhibiting acid phosphatase from Francisella tularensis.

Acid phosphatases (Acp) of intracellular pathogens have recently been implicated as virulence factors that enhance intracellular survival through suppression of the respiratory burst. We describe here the identification, purification, characterization, and sequencing of a novel burst-inhibiting acid phosphatase from the facultative intracellular bacterium, Francisella tularensis. Similar to other the burst-inhibiting Acps, F. tularensis Acp (AcpA) is tartrate-resistant and has broad substrate specificity. The AcpA enzyme is unique, however, in that it is easily released from the bacterial cell in soluble form, is a basic enzyme, suppresses the respiratory burst of not only fMet-Leu-Phe but also phorbol 12-myristate 13-acetate-stimulated neutrophils and does not fit into any of the three currently recognized classes of acid phosphatase. We also report the complete nucleotide sequence of the gene acpA, encoding AcpA, and the deduced primary structure of its encoded polypeptide. Comparative sequence analyses of AcpA is discussed. To our knowledge, this is the first report describing the cloning and sequencing of a burst-inhibiting acid phosphatase.

Acid Phosphatase↗
PubMed1980

Rapid, fully automated radioimmunoassay of prostatic acid phosphatase in serum.

Prostatic acid phosphatase was purified from human semen and its purity established by biochemical and immunological criteria. Rabbits were injected with the purified isoenzyme to raise specific antisera. The prostatic acid phosphatase was radiolabeled with 125I by the Chloramine T method. We developed a fully automated double-antibody radiommunosassay for measuring prostatic acid phosphatase in serum from patients with carcinoma of the prostate and from several control groups. The lower detection limit of the radioimmunoassay was 2.0 microgram of prostatic acid phosphatase per litre of serum. Values for most members of the control group was <2.0 microgram/L; patients with metastatic carcinoma of the prostate had values ranging from <2.0 to 300 microgram/L of serum.

Acid Phosphatase↗
PubMed1992

Modification of the effects of hyperthermia and neutron radiation on the activity of acid phosphatase in CaNT tumors.

Acid phosphatase activity was measured in implanted murine CaNT tumors of varying volumes. There is a clear monotonically increasing relation between acid phosphatase activity and tumor volume. Also the tumors were subjected to either induced artificial hypoxia or hyperthermia (41.0 degrees C) alone, or combined with neutron irradiation (3.8 Gy). Changes in the activity of this enzyme following radiation damage could reflect tissue damage associated with metabolic disturbances. The effect on enzyme activity after sequential hyperthermia and neutron irradiation is not synergistic, as is shown in the quantitative experimental data. This implies that the mechanisms of heat damage differ from that of neutron beam damage, as reflected by acid phosphatase activity. The CaNT tumor was also shown to be thermosensitive after administration of mitoxantrone. Finally, the role of exogenous ATP was shown to provide heat protection by modification of those thermal effects resulting in the activity of acid phosphatase. The augmentation of this hydrolytic enzyme probably represents initial metabolic damage in the tumor after different modalities of radiation alone, or combined with mitoxantrone and exogenous ATP.

Acid Phosphatase↗
PubMed1997

Identification of a protein-tyrosine phosphatase (SHP1) different from that associated with acid phosphatase in rat prostate.

Using [32P]poly(Glu,Tyr) as substrate, we have identified, for the first time, in the rat prostatic gland a protein-tyrosine phosphatase activity different from that associated with prostatic acid phosphatase. Concanavalin A-Sepharose 4B was used to separate the two protein-tyrosyl phosphatases activities. The activity retained by the lectin had characteristics of the prostatic acid phosphatase. It was sensitive to inhibition by PNPP and the optimum pH shifted towards physiological values when [32P]poly(Glu,Tyr) was used as substrate. However, the major protein-tyrosine phosphatase activity was not retained by the lectin, and corresponded, at least in part, to SHP1 as probed by the presence of the protein, its mRNA and the loss of PTPase activity after immunodepletion of SHP1. This enzyme is localized within the epithelial cells. Thus, the coexistence of two protein-tyrosine phosphatase activities in rat prostate, one associated with the acid phosphatase and the other related to SHP1, makes it necessary to analyze the importance of both activities in vivo and their possible function regarding prostatic cell growth and its regulation.

Acid Phosphatase↗
PubMed1999

The human and rat forms of multiple inositol polyphosphate phosphatase: functional homology with a histidine acid phosphatase up-regulated during endochondral ossification.

We have derived the full-length sequences of the human and rat forms of the multiple inositol polyphosphate phosphatase (MIPP); their structural and functional comparison with a chick histidine acid phosphatase (HiPER1) has revealed new information: (1) MIPP is approximately 50% identical to HiPER1, but the ER-targeting domains are divergent; (2) MIPP appears to share the catalytic requirement of histidine acid phosphatases, namely, a C-terminal His residue remote from the RHGxRxP catalytic motif; (3) rat MIPP mRNA is up-regulated during chondrocyte hypertrophy. The latter observation provides a context for proposing that MIPP may aid bone mineralization and salvage the inositol moiety prior to apoptosis.

Acid Phosphatase↗
PubMed1989

Inhibition of osteoclastic acid phosphatase abolishes bone resorption.

Osteoclastic acid phosphatase is a member of a widely-distributed class of iron-containing proteins with acid phosphatase activity. Antibodies raised against one member of this class cross-react with other members from the same or different species, but not with acid phosphatase isoenzymes of different types. When antibodies to one such protein, porcine uteroferrin, are added to medium in which rat osteoclasts are incubated on devitalised cortical bone, both bone resorption and acid phosphatase activity are markedly inhibited. Furthermore, addition of molybdate (an inhibitor of this class of acid phosphatases) also inhibits both bone resorption and enzyme activity. These observations strongly suggest a functional role for osteoclastic acid phosphatase in bone resorption.

Acid Phosphatase↗
PubMed1980

Purification and characterization of acid phosphatase from Dunning R3327H prostatic adenocarcinoma.

Acid phosphatase (phosphoric monoester hydrolase) was isolated from the Dunning R3327H prostatic adenocarcinoma, a slow-growing and hormone-sensitive rat prostate tumor histologically similar to well-differentiated human prostatic cancer. The enzyme was purified to homogeneity and characterized. In comparison with the acid phosphatase isolated from human malignant prostate, the acid phosphatase from the Dunning rat tumor was similar in molecular weight [100,000 +/- 10% (S.D.)]. However, it possessed a single isoelectric point of 7.6 (human prostatic acid phosphatase showed multiple isoenzymes at 4.4 to 5.3); an electrophoretic mobility of 0.5 in reference to human prostatic acid phosphatase on 7.5% polyacrylamide gel, pH 8.5; an optimal pH of 5.0 with alpha-naphthyl phosphate as the substrate in 0.1 M citrate buffer (human prostatic acid phosphatase, 5.5); and a Km (alpha-naphthyl phosphate) of 6.9 X 10(-4) M (human prostatic acid phosphatase, 4.4 X 10(-5) M). Furthermore, it did not cross-react with antiserum raised against human prostatic acid phosphatase. These results show that the acid phosphatase of the Dunning R3327H prostatic adenocarcinoma is biochemically and immunologically distinct from human prostatic acid phosphatase and may be unique for this animal model of prostatic cancer.

Acid Phosphatase↗
PubMed1999

Crystal structure of a mammalian purple acid phosphatase.

Tartrate-resistant acid phosphatase (TRAP) is a mammalian di-iron- containing enzyme that belongs to the family of purple acid phosphatases (PAP). It is highly expressed in a limited number of tissues, predominantly in bone-resorbing osteoclasts and in macrophages of spleen. We have determined the crystal structure of rat TRAP in complex with a phosphate ion to 2.7 A resolution. The fold resembles that of the catalytic domain of kidney bean purple acid phosphatase (KBPAP), although the sequence similarity is limited to the active site residues. A surface loop near the active site is absent due to proteolysis, leaving the active-site easily accessible from the surrounding solvent. This, we believe, gives a structural explanation for the observed proteolytic activation of TRAP. The current structure was determined at a relatively high pH and without any external reducing agents. It is likely that it represents an oxidized and therefore catalytically inactive form of the enzyme.

Acid Phosphatase↗
PubMed2006

Alteration of adenoid tissue alkaline and acid phosphatase in children with secretory otitis media.

OBJECTIVE: The role of pharyngeal lymphoid tissue in etiopathogenesis of secretory otitis is not yet defined. The influence of tonsillar and adenoid mass, weight, obstruction of naspharyngeal orrifitium, bacterial reservoire or some immunological events are of scientific interest. Tissue nonspecific alkaline phosphatase (TNAP) and acid phosphatase (ACP) are enzymes detected in lymphoid tissue, TNAP as characteristic of B cells, ACP as a characteristic of macrophages and folucullardentritic cells. These enzymes interfere in cell metabolism by removing 5' phosphate group from nucleotides and proteins. Specific activity and kinetic properties were studied in palatinal tonsils and adenoids of children with secretory otitis (OME) and compared with children with recurrent tonsillitis without ear involvement. METHOD: Adenoid and tonsillar tissue of l7 children with OME and 30 children with recurrent tonsillitis were subjected to biochemical investigation using method of releasing of p-nitrophenol from p-nitrophenylphosphate (pNPP). Kinetic parameters as Michaelis-Menten constant were calculated by non-linear regression estimation method. RESULTS: Specific activity of adenoid alkaline phosphatase was lower in children with OME in relation to children with recurrent tonsillitis (t=5.733507, p<0.01). Specific activity of adenoid acid phosphatase was also lower in children with OME (t=3.655456, p<0.01). pH optimum for both enzymes was the same in these two groups of children. Michaelis-Menten constant for both enzymes was significantly higher in adenoid of children with OME than in children with recurrent tonsillitis suggesting lower enzyme affinity for the substrate. CONCLUSION: Differences in specific activities and kinetic properties of adenoid alkaline and acid phosphatases between children with OME and children with recurrent tonsillitis without OME were verified in this study. The results of the study are not able to explain the alteration of alkaline and acid phosphatase characteristics but could point to some possible and specific role of nasopharyngeal lymphoid tissue in pathogenesis of secretary otitis.

Acid Phosphatase↗