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PubMed2004

Prostatic acid phosphatase degrades lysophosphatidic acid in seminal plasma.

Lysophosphatidic acid (LPA) is a lipid mediator with multiple biological activities and is detected in various biological fluids, including human seminal plasma. Due to its cell proliferation stimulatory and anti-apoptotic activities, LPA has been implicated in the progression of some cancers such as ovarian cancer and prostate cancer. Here, we show that prostatic acid phosphatase, which is a non-specific phosphatase and which has been implicated in the progression of prostate cancer, inactivates LPA in human seminal plasma. Human seminal plasma contains both an LPA-synthetic enzyme, lysoPLD, which converts lysophospholipids to LPA and is responsible for LPA production in serum, and its major substrate, lysophosphatidylcholine. In serum, LPA accumulated during incubation at 37 degrees C. However, in seminal plasma, LPA did not accumulate. This discrepancy is explained by the presence of a strong LPA-degrading activity. Incubation of LPA with seminal plasma resulted in the disappearance of LPA and an accompanying accumulation of monoglyceride showing that LPA is degraded by phosphatase activity present in the seminal plasma. When seminal plasma was incubated in the presence of a phosphatase inhibitor, sodium orthovanadate, LPA accumulated, indicating that LPA is produced and degraded in the fluid. Biochemical characterization of the LPA-phosphatase activity identified two phosphatase activities in human seminal plasma. By Western blotting analysis in combination with several column chromatographies, the major activity was revealed to be identical to prostatic acid phosphatase. The present study demonstrates active LPA metabolism in seminal plasma and indicates the possible role of LPA signaling in male sexual organs including prostate cancer.

Acid Phosphatase↗
PubMed1995

Unique structural features of red kidney bean purple acid phosphatase.

Purple acid phosphatase from red kidney beans (Phaseolus vulgaris) has been purified to homogeneity and characterized. The enzyme is a homodimer of 60 kDa subunits each containing one atom of zinc and iron in the active site. Circular dichroism spectral studies on the purified enzyme reveals that a large portion of the peptide backbone is in the unordered and beta-turn conformation. A unique feature of the red kidney bean acid phosphatase, which we have found, is that one of the two cysteines of each subunit is involved in the formation of an inter-subunit disulphide. The thiol group of the other cysteine is not necessary for the activity of the enzyme. Western blot analysis with antibodies raised against kidney bean acid phosphatase could not recognize acid phosphatases from other sources except from potato. This paper emphasizes the fact that acid phosphatases are functionally, but not structurally, conserved enzymes.

Acid Phosphatase↗
PubMed1991

Isolation and characterization of a homogeneous isoenzyme of wheat germ acid phosphatase.

An acid phosphatase (orthophosphoric monoester phosphohydrolase, acid optimum; EC 3.1.3.2) isoenzyme from wheat germ was purified 7000-fold to homogeneity. The effect of wheat germ sources and their relationship to the isoenzyme content and purification behavior of acid phosphatases was investigated. Extensive information about the purification and stabilization of the enzyme is provided. The instability of isoenzymes in the latter stages of purification appeared to be the result of surface inactivation together with a sensitivity to dilution that could be partially offset by addition of Triton X-100 during chromatographic procedures. Added sulfhydryl protecting reagents had no effect on activity or stability, which was greatest in the pH range 4-7. The purified isoenzyme was homogeneous by polyacrylamide gel electrophoresis and exhibited the highest specific activity and turnover number reported for any acid phosphatase. The molecular weights of the pure isoenzyme and of related isoenzymes from wheat germ were found to be identical (58,000). The pure isoenzyme contained a single polypeptide chain and had a negligible carbohydrate content. The amino acid composition was determined. Of the various reasons that were considered to explain isoenzyme occurrence, a genetic basis was considered most likely. The enzyme was found to exhibit substrate inhibition with some substrates below pH 6, while above pH 8 it exhibited downwardly curving Lineweaver-Burk plots of the type that are generally described as "substrate activation". The observation of a phosphotransferase activity was consistent with the formation of a covalent phosphoenzyme intermediate, while inactivation by diethyl pyrocarbonate was consistent with the presence of an active site histidine.

Acid Phosphatase↗
PubMed2004

Phosphotyrosyl peptides and analogues as substrates and inhibitors of purple acid phosphatases.

Purple acid phosphatases are metal-containing hydrolases. While their precise biological role(s) is unknown, the mammalian enzyme has been linked in a variety of biological circumstances (e.g., osteoporosis) with increased bone resorption. Inhibition of the human enzyme is a possible strategy for the treatment of bone-resorptive diseases such as osteoporosis. Previously, we determined the crystal structure of pig purple acid phosphatase to 1.55A and we showed that it is a good model for the human enzyme. Here, a study of the pH dependence of its kinetic parameters showed that the pig enzyme is most efficient at pH values similar to those encountered in the osteoclast resorptive space. Based on the observation that phosphotyrosine-containing peptides are good substrates for pig purple acid phosphatase, peptides containing a range of phosphotyrosine mimetics were synthesized. Kinetic analysis showed that they act as potent inhibitors of mammalian and plant purple acid phosphatases, with the best inhibitors exhibiting low micromolar inhibition constants at pH 3-5. These compounds are thus the most potent organic inhibitors yet reported for the purple acid phosphatases.

Acid Phosphatase↗
PubMed1976

Removal of phosphate groups from casein with potato acid phosphatase.

Potato acid phosphatase (EC 3.1.3.2) was used to remove the eight phosphate groups from alphas1-casein. Unlike most acid phosphatases, which are active at pH 6.0 or below, potato acid phosphatase can catalyze the dephosphorylation of alphas1-casein at pH 7.0. Although phosphate inhibition is considerable (K1=0.42 mM phosphate), the phosphate ions produced by the dephosphorylation of casein can be removed by dialysis, allowing the reaction to go to completion. The dephosphorylated alphas1-casein is homogeneous on gel electrophoresis with a slower mobility than native alphas1-casein and has an amino acid composition which is identical to native alphas1-casein. Thus the removal of phosphate groups from casein does not alter its primary structure. Potato acid phosphatase also removed the phosphate groups from other phosphoproteins, such as beta-casein, riboflavin binding protein, pepsinogen, ovalbumin, and phosvitin.

Acid Phosphatase↗
PubMed1982

Immunohistochemical identification of prostatic acid phosphatase: correlation of tumor grade with acid phosphatase distribution.

The localization and distribution of prostatic specific acid phosphatase (PSAP) in normal, hyperplastic and neoplastic prostates were studied by specific immunohistochemical of normal and hyperplastic prostates. In adenocarcinoma of the prostate, a correlation of the PSAP staining with the degree of differentiation and the ability of the tumor to form a gland was observed: more intense and uniform staining in well differentiated tumors and less intense and more variable stains in poorly differentiated tumors. The same correlation was also observed in tumors metastasized to lymph nodes and other organs.

Acid Phosphatase↗
PubMed1985

Cytochemistry and biochemistry of acid phosphatases V: Electrophoretic studies on the heterogeneity of acid phosphatases from human prostate, seminal fluid, and leukocytes.

Comparison of zymograms of acid phosphatases (orthophosphoric monoester phosphohydrolase, acid optimum, E.C.3.1.3.2) from human prostate, leukocytes, seminal vesicles, and seminal fluid, separated by analytical isoelectric focusing (IEF), resulted in the identification of three individual groups, particularly of the prostate. These groups contain three molecular forms at different molecular weights and activities in varying quantities and combinations. The molecular weights, estimated by SDS gel electrophoresis, were 1) 86,000, 2) 76,000, and 3) 46,000/50,000 (in a doublet) daltons. None of these isoenzymes were restricted to the prostate, but they were present in very high concentrations in the prostate. Compared to the prostate, the seminal vesicles and isolated leukocytes had very closely related zymograms of acid phosphatases. No specific inhibitor has been found that would selectively inhibit one particular isoenzyme without affecting the others. Protein titration and staining activity of IEF gels at different pH values showed that the isoenzymes from all three groups have high hydrolytic activity of orthophosphoric monoesters beyond the acidic pH range of pH 4-5. Incubation of acidic isoforms of acid phosphatases with neuraminidase did not result in the formation of a homogeneous stem molecule. Further analysis of the secretory moiety using the western blotting method showed a binding of peroxidase-conjugated concanavalin A (Con A), indicating that these isoenzymes are glycoproteins. Moreover, isoenzymes extracted from prostate, seminal fluid, and human leukocytes are immunologically identical.

Acid Phosphatase↗
PubMed1986

Evolution of localization of the reactions of adenosine triphosphatase (Mg++-ATP-ase), 5'nucleotidase (5'nt), alkaline phosphatase (AP), and acid phosphatase (AcP) in developing rat testis. I. Physiological conditions.

The experiments were performed upon the rats aged 1, 4, 7, 15, 30, 45, 60, 90 d, and 1,5 a. The behavior of the following reactions was described: for adenosine triphosphatase stimulated by Mg++(Mg++-ATP-ase), for 5'nucleotidase (5'Nt), for alkaline phosphatase (AP), for acid phosphatase (AcP). The first 3 are markers of the transport enzymes in cells, and the 4th is a marker of lytic processes. It was estimated on the basis of the examined reactions that a full metabolic maturity of the gonad was revealed since the 45th d of post-fetal life.

5'-Nucleotidase↗
PubMed1998

Kinetics of inhibition of Penaeus penicillatus acid phosphatase by bromoacetic acid.

The kinetics of inhibition of penaeus penicillatus acid phosphatase by bromoacetic acid has been studied. The results show that inhibition of the enzyme by bromoacetic acid is a slow, reversible reaction. The microscopic rate constants for the reaction of inhibitor with the enzyme were determined. The presence of the substrate offers marked protection of this enzyme against inhibition by bromoacetic acid. The above results suggest that the histidine residue is essential for activity and are situated at the active site of the enzyme.

Acetates↗
PubMed2006

Identification and molecular modeling of a novel, plant-like, human purple acid phosphatase.

Purple acid phosphatases are a family of binuclear metallohydrolases that have been identified in plants, animals and fungi. Only one isoform of approximately 35 kDa has been isolated from animals, where it is associated with bone resorption and microbial killing through its phosphatase activity, and hydroxyl radical production, respectively. Using the sensitive PSI-BLAST search method, sequences representing new purple acid phosphatase-like proteins have been identified in mammals, insects and nematodes. These new putative isoforms are closely related to the approximately 55 kDa purple acid phosphatase characterized from plants. Secondary structure prediction of the new human isoform further confirms its similarity to a purple acid phosphatase from the red kidney bean. A structural model for the human enzyme was constructed based on the red kidney bean purple acid phosphatase structure. This model shows that the catalytic centre observed in other purple acid phosphatases is also present in this new isoform. These observations suggest that the sequences identified in this study represent a novel subfamily of plant-like purple acid phosphatases in animals and humans.

Acid Phosphatase↗
PubMed2003

Phosphorylation and dephosphorylation of polyhydroxy compounds by class A bacterial acid phosphatases.

Nonspecific acid phosphatases share a conserved active site with mammalian glucose-6-phosphatases (G6Pase). In this work we examined the kinetics of the phosphorylation of glucose and dephosphorylation of glucose-6-phosphate (G6P) catalysed by the acid phosphatases from Shigella flexneri (PhoN-Sf) and Salmonella enterica (PhoN-Se). PhoN-Sf is able to phosphorylate glucose regiospecifically to G6P, glucose-1-phosphate is not formed. The K(m) for glucose using pyrophosphate (PPi) as a phosphate donor is 5.3 mM at pH 6.0. This value is not significantly affected by pH in the pH region 4-6. The K(m) value for G6P by contrast is much lower (0.02 mM). Our experiments show these bacterial acid phosphatases form a good model for G6Pase. We also studied the phosphorylation of inosine to inosine monophosphate (IMP) using PPi as the phosphate donor. PhoN-Sf regiospecifically phosphorylates inosine to inosine-5'-monophosphate whereas PhoN-Se produces both 5'IMP and 3'IMP. The data show that during catalysis an activated phospho-enzyme intermediate is formed that is able to transfer its phosphate group to water, glucose or inosine. A general mechanism is presented of the phosphorylation and dephosphorylation reaction catalysed by the acid phosphatases. Considering the nature of the substrates that are phosphorylated it is likely that this class of enzyme is able to phosphorylate a wide range of hydroxy compounds.

Acid Phosphatase↗
PubMed1985

Tartrate-resistant acid phosphatase of human lung: apparent identity with osteoclastic acid phosphatase.

Extracts of human lung tissue contain appreciable activities of a tartrate-resistant acid phosphatase which is apparently identical with the analogous enzyme in bone extracts, with respect to electrophoretic mobility, apparent molecular weight (ca. 37,000), Michaelis constants and relative rates of hydrolysis of various substrates. The acid phosphatase appears to be a constituent of alveolar macrophages. Lung provides a convenient source for the preparation of tartrate-resistant acid phosphatase.

Acid Phosphatase↗
PubMed1981

Cytochemical studies on the ferritin-containing vesicles of the rat incisor ameloblasts with special reference to the acid phosphatase activity.

Acid phosphatase was localized in rat incisor ameloblasts without prior decalcification. When beta-glycerophosphate was used as the substrate, an intense reaction was observed in the supranuclear region of the secretory ameloblasts. But the reaction was dramatically reduced at the transitional stage and was very weak in the maturation ameloblasts. When p-nitrophenylphosphate was the substrate, the reaction product was consistently seen in the Golgi cisternae and the vesicular components of the ameloblasts at all stages of enamel development. These observations suggest that there are two acid phosphatases in ameloblasts. One is in the secretory ameloblasts and the other in the transition and maturation ameloblasts. X-ray microanalyses for Fe and Pb showed that Fe and acid phosphatase were in the ferritin-containing vesicles at the later stage of enamel maturation. This evidence suggests that ferritin is digested in these vesicles for the release of the Fe pigment to the enamel. An increase in the number of intercellular bridges between ameloblasts was correlated with the dramatic decrease in height of ameloblasts at the pigment release stage. The ameloblast membranes were acid phosphatase positive at the intercellular bridges when p-nitrophenylphosphate was the substrate. This activity may be involved in the reduction in the surface area of the ameloblast membranes.

4-Nitrophenylphosphatase↗