Acid phosphomonoesterase of human prostate. Carbohydrate content and optical properties

Hyperalkaline and thermostable phosphatase in Thermus thermophilus

The phosphatases existing in the extreme thermophilic bacterium Thermus thermophilus have been studied. Utilizing ion exchange, hydrophobic, pseudoaffinity, and affinity chromatography, a number of distinct phosphatase activities were identified. At least four phosphatases, with optimum pH ranging between 5.0 and 11.5, were assayed with p-nitrophenylphosphate, and two with optimum pH between 7.0 and 11.0, with 32P-casein as substrate. The authors have focused on the hyperalkaline phosphatase and have tried to purify and characterize it. This hyperalkaline phosphatase reaches a maximal level at the stationary phase of the growth, and is co-purified with alkaline phosphatase with optimum pH of 10.2. The enzymes present a relative mol wt of 65 and 58 kDa, respectively, as judged by SDS-PAGE and Sephadex G-150 column, and possess similar properties, indicating that they are isoforms. These enzymes barely function in the presence of tartrate, and are inhibited by EDTA, pyrophosphate, and molybdate. Among the metals tested, Hg2+ appeared as the strongest inhibitor of the hyperalkaline phosphatase. The two enzymes are thermostable and, upon treatment at 90 degrees C for 10 min, 75% of their activity remains. The physiological role and function of these phosphatases need further investigation.

Human tissue non-specific alkaline phosphatases: sugar-moiety-induced enzymic and antigenic modulations and genetic aspects

To investigate the possible role(s) of glycans in human tissue non-specific alkaline phosphatase (TNAP) activity, the iso-enzymes were purified and treated with various exo- and endo-glycosidases. Catalytic activity, oligomerization, conformation and immunoreactivity of the modified TNAPs were evaluated. All TNAPs proved to be N-glycosylated, and only the liver isoform (LAP) is not O-glycosylated. Usually, the kidney (KAP) and bone (BAP) isoenzymes are similar and cannot be clearly discriminated. Differences between the immunoreactivity of KAP/BAP and LAP with a BAP antibody were mainly attributed to the N-glycosylated moieties of the TNAPs. In addition, elimination of O-glycosylations moderately affects the TNAP reactivity. Interestingly, N-glycosylation is absolutely essential for TNAP activity, but not for that of the placental or intestinal enzymes. According to the deduced amino acid sequence of TNAP cDNA, Asn-213 is a possible N-glycosylation site, and our present findings suggest that this sugar chain plays a key role in enzyme regulation. With regard to the oligomeric state of alkaline phosphatase (AP) isoforms, the dimer/tetramer equilibrium is dependent on the deglycosylation of glycosyl-phosphatidylinositol(GPI)-free APs, but not GPI-linked APs. This equilibrium does not affect the AP conformation as observed with CD. With regard to TNAPs, no data were available on the gene expression or nature of the 5'-non-translated leader exon of human KAP, as opposed to BAP and LAP genes. cDNA sequencing revealed that cortex/medulla KAP is genetically related to BAP, and medulla KAP to LAP.

Clinical and biological aspects of acid phosphatase

The identity and genetic origins of the nonspecific orthophosphate monoesterases with an acid pH optimum--the acid phosphatases--are now becoming clear. They form a family of genetically distinct isoenzymes, many of which show significant posttranslational modification. Four true isoenzymes exist. The erythrocytic and lysosomal forms show widespread distribution and are expressed in most cells; in contrast, the prostatic and macrophagic forms have a more limited expression. The erythrocytic and macrophagic forms are distinguished from the others in resisting inhibition by dextrorotatory tartrate. The prostatic form has long been used as a marker for prostatic cancer and the macrophagic forms have been linked with miscellaneous disorders, notably increased osteolysis, Gaucher's disease of spleen, and hairy cell leukemia, whereas the normal levels of intravesical lysosomal acid phosphatase in I cell disease pointed the way toward the mechanisms underlying its intracellular processing.

A reference preparation of human prostatic acid phosphatase: purification, characterization and field trials

Acid phosphatase has been prepared in an apparently pure state by affinity chromatography from human prostatic tissue. When dissolved in an acidic albumin solution, lyophilized and stored at -20 degrees C for up to 2 years, no time-dependent loss of catalytic activity was detectable in the reconstituted material. Accelerated degradation tests also predicted complete stability. A preliminary distribution of the lyophilized preparation to 143 laboratories confirmed its robustness and demonstrated its potential usefulness as a calibrant to unify the results of different methods of measuring acid phosphatase activity.

Prostate-specific antigen and prostatic acid phosphatase: biomolecular and physiologic characteristics

PSA is a 34-kd 240-amino acid glycoprotein produced by the prostatic epithelial cells. It is a member of the glandular kallikrein gene family and has a high sequence homology with human glandular kallikrein (hGK-1). PSA is a serine protease and has chymotrypsin-, trypsin-, and esterase-like activities. It is secreted into the seminal fluid where it degrades two seminal vesicle proteins that are important components of the semen coagulum, thus playing an important role in semen liquefaction. The production of PSA protein appears to be under the control of circulating androgens acting through the androgen receptor. Therefore, the significance of a low serum PSA value in a patient who has undergone previous antiandrogen therapy may not be the same as that for a patient who has not received endocrine treatment.

Studies on the oligosaccharide heterogeneity of the isoelectric forms of the lower molecular weight acid phosphatase of frog liver

1. The lower molecular weight, heterogeneous acid phosphatase (AcPase) from the frog liver (Rana esculenta) containing AcPase I, II, III and IV was separated into enzymatically active components by isoelectric focusing in an immobilized pH gradient. 2. The blotted enzyme bands were characterized by their different binding patterns obtained with the lectins concanavalin A, wheat germ agglutinin (WGA), Lens culinaris hemagglutinin (LcH) and peanut agglutinin (PNA). 3. In situ neuraminidase treatment reduced the staining intensity of some WGA-bands and increased that of PNA-bands. 4. The finding that AcPases I, II, III and IV differ in their carbohydrate chain composition, together with previous results showing different bioactivities of AcPases III and IV, indicates a correlation between the glycosylation state of enzyme forms and their physiological action.

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.

Relationship of prostatic acid phosphatase localization in human prostate by a monoclonal antibody with the Gleason grading system

Prostatic acid phosphatase (PAP) was localized in human prostate with a monoclonal antibody prepared against PAP isoenzyme II to determine patterns of its expression in normal, hyperplastic (BPH), and cancerous glands. The monoclonal antibody reacted with both isoenzymes II and IV in immunoblot studies. Formalin-fixed, paraffin-embedded tissue was used from patients who had not been treated with hormones or chemotherapy. In normal glands and BPH, there was marked variation in the intensity of PAP staining in morphologically otherwise similar epithelial cells. There was similar heterogeneity of staining in the adenocarcinomas. Rough quantification of the intensity patterns in the clinical groups indicated a slight shift to more intense staining in BPH and well-differentiated carcinomas but a progressive decline in the PAP staining in the moderately and poorly differentiated tumors. This decrease in intracellular staining with decreasing differentiation is not inconsistent with the clinical observation that serum levels of acid phosphatase generally increase with higher grade and disseminated tumors, since the enzyme is simply more accessible to the circulatory system in those cases. The same decrease may explain the few disseminated tumors that are not associated with elevated serum levels.

Structures of the carbohydrate moieties of human prostatic acid phosphatase elucidated by H1 nuclear magnetic resonance spectroscopy

The structures of the oligosaccharides comprising the carbohydrate moieties of human prostatic acid phosphatase were elucidated by 1H NMR spectroscopy. Homogeneous enzyme was digested with Pronase P, and three asparagine-linked carbohydrate moieties were obtained upon fractionation of the digest using a concanavalin A-Sepharose affinity column. One fraction did not bind to the column, while the portion that did bind was separated into two fractions by elution with two concentrations of mannose. The high-resolution 1H NMR spectra for the three fractions were recorded at 470 MHz. From these data, the structures were deduced to be high mannose, partially sialylated and fucosylated biantennary complex, and fucosylated, partially sialylated triantennary complex oligosaccharides. No O-linked carbohydrate moiety was detected, although the possible presence of small O-linked oligosaccharides cannot be completely discounted from these data.

Catfish liver acid phosphatases: differently glycosylated enzyme molecules with altered kinetic properties

Two forms of catfish liver acid phosphatase (AcPase I and II) were separated and purified to homogeneity and their carbohydrate compositions and some biochemical properties were studied. Evidence is given that AcPase I and II are differently glycosylated forms of the same enzyme. The enzyme forms differ significantly in the size and the composition of their carbohydrate components, sensitivity towards sulfhydryl-blocking and protecting reagents, sensitivity to ferric and ferrous ions, thermostability and ability to hydrolyze some nucleotides. The more highly glycosylated form is more sensitive to thermal denaturation. AcPase I and II behave differently towards ascorbate and changes in its concentration and it is suggested that the concentration of reducing modifiers may regulate AcPase activity at the cellular level. It is hypothesized that the differing extents of glycosylation influence the structure of the enzyme forms. This is expressed in altered conformations of two enzyme forms and results in a different exposure of the essential cysteine residues.

Monoclonal antibody specific to acid phosphatase isoenzyme 4

Prostatic acid phosphatase isoenzyme 4 was purified by ion exchange column chromatography, followed by high pressure liquid chromatography. The highly purified enzyme was used to produce monoclonal antibody from immunized BALB/c mice. The antibody was specific to isoenzyme 4, with negligible affinity to isoenzyme 2. The specificity of the monoclonal antibody was evaluated by Western blot analysis and by inhibition of radioimmunoassay. Immunohistochemistry method using the antibody to isoenzyme 2 showed heavy staining on the cell surface in contrast to the even staining throughout the cytoplasm when monoclonal anti-isoenzyme 4 was used. These results reflect the secretory nature of isoenzyme 2 and the non-secretory nature of isoenzyme 4.

Immunological characterization of human acid phosphatase gene products

The immunological cross-reactivity of heterogeneous acid phosphatase isozymes from different human tissues has been studied using monospecific antisera prepared against four homogeneous acid phosphatases. The enzyme characterized as tartrate-inhibitable, prostatic acid phosphatase is also found to be present in leukocytes, kidney, spleen, and placenta. The tartrate-inhibitable (liver) lysosomal enzyme is also found in kidney, fibroblasts, brain, placenta, and spleen, but it is not detectable in erythrocytes and prostate. In several tissues, 10-20% of the tartrate-inhibitable enzyme is not precipitated by any of the antisera used; an exceptionally high amount (54%) of such an enzyme is present in human brain. Antiserum against a low molecular weight tartrate-resistant liver enzyme (14 kDa) does not crossreact with the erythrocyte enzyme. (10-20 kDa). All other tissues except placenta, prostate, and fibroblast cells show a cross-reactivity with the 14-kDa acid phosphatase antiserum. Thus, the low molecular weight human liver acid phosphatase is distinct from the erythrocyte enzyme, and there are also at least three different tartrate-inhibitable acid phosphatases in human tissues. Chromosomal assignments have been made for only two of the (at least) five acid phosphatases that are present in adult human tissues.

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.

Studies of the heterogeneity of carp liver acid phosphatases: acid phosphatase--I. Subunit structure and carbohydrate composition

The three molecular forms of the carp liver acid phosphatase (AcPase) were shown to be dimeric proteins, two of them differing in molecular weights. An activating effect of ConA binding on the AcPases has been observed. AcPase I and AcPase II showed a mol. wt of 122,500 and of 58,884 +/- 3000 for their subunits. It is assumed that AcPase I is a sialylated derivative of AcPase II. AcPase III has a mol. wt of 93,132 and the two subunits of 46,556 +/- 4000. A homogeneous AcPase I was obtained and its carbohydrate composition is presented.

Human prostatic acid phosphatase: properties of the native enzyme, and the enzyme-antibody complex

Acid phosphatase purified from human prostatic tissue was shown to be homogeneous by polyacrylamide gel electrophoresis and N-terminal amino acid analysis. However, isoelectric focusing revealed a large number of isoenzymes which were reduced to four by digestion with neuraminidase. It is suggested that the patterns observed are due to differences in bound carbohydrate attached to the same protein backbone. Antiserum to the purified enzyme was produced in rabbits and reacted with the enzyme to form an enzymatically active complex of large molecular weight. This complex is more stable at high temperatures than the native enzyme. Kinetic analysis of both the enzyme and the enzyme-antibody complex demonstrated that the binding of the antibody caused no significant change to the active site of the enzyme.

Human prostatic acid phosphatase: purification, characterization, and optimization of conditions for radioimmunoassay

Prostatic acid phosphatase was isolated from benign hypertrophic prostate tissue by ammonium sulfate precipitation and affinity chromatography procedures. The purified enzyme was characterized by two-dimensional gel electrophoresis and shown to have a cluster of protein spots with an apparent molecular weight of 48 000 at pI 5.9 to 6.3 in 9 mol/l urea. The specific activity of the purified enzyme was 723 and 659 U/mg protein with alpha-naphthyl phosphate at 30 degrees C and para-nitrophenyl phosphate at 37 degrees C respectively. An antibody to the purified enzyme was raised in rabbits and used in a radioimmunoassay (RIA). The use of a phosphate buffer, pH 6.6, and iodination of prostatic acid phosphatase (PAP) by the Bolton-Hunter procedure improved the precision of the assay when compared to RIA's using a phosphate buffer, pH 7.0 or 7.3, or PAP iodinated by a chloramine-T procedure. The former RIA displaced 50% of the tracer at 2 micrograms of enzyme per liter of serum. The between-run coefficient of variation for 11 assays ranged from 3.9-7.7% with serum at 1.3 to 5.6 micrograms PAP/l.

Comparison of prostatic and nonprostatic acid phosphatase

Electrophoresis and ion-exchange column chromatography were used to separate the wide varieties of acid phosphatases with different biological and clinical significance. Band 0 was very strong in ascitic cells with many autophagic vacuoles, indicating a role in autophagic function. Band 1 was a membrane-bound acid phosphatase, seen mainly in the microsomal fraction. Band 3 was the major lysosomal acid phosphatase of all nonprostatic tissues. Bands 2 and 4 were antigenically identical to each other, and were observed in unusually high amounts in the prostate. The different electrophoretic mobility between bands 2 and 4 was due to their carbohydrate content. Band 5 was a characteristic enzyme of the osteoclast. The tartrate-sensitive enzymes included bands 0 through 4. Only band 5 was tartrate resistant. The tartrate-resistant acid phosphatase of erythrocytes was not detected by the electrophoresis method. Clinical applications were seen for both bands 2 and 5. Band 2 was a secretory enzyme, normally secreted into the seminal plasma. Band 2 was absorbed into the blood circulation in some prostatic cancer patients. A small amount of bands 2 and 4 was observed in nonprostatic tissues. The diagnostic value of band 2 resulted from its extremely high concentration in the prostate. Band 5 was not observed in the normal prostate. A high concentration of band 5 was observed in hairy cells, Gaucher cells, and osteoclasts. The serum level of band 5b was an indicator of osteoclastic activity in the bone. Elevation of band 5b in serum was observed in normal children during physiological bone growth, in Gaucher's disease, and in malignancies metastasized to bone.

Isolation, characterization, and spontaneous interconversion of two forms of human prostatic acid phosphatase

Starting with human prostatic acid phosphatase (HPAP) purified by affinity chromatography on Sepharose-bound N-(6-aminohexyl)tartramic acid [Van Etten, R. L. and Saini, M. S. (1978) Clin. Chem. 24, 1525], two forms of the enzyme can be separated by gradient elution DEAE-cellulose chromatography. The two enzyme forms are electrophoretically distinguishable on high pH gels. Under some conditions of storage one of these forms undergoes a conversion to the other. Both forms have identical amino acid compositions and Vmax values with typical substrates, but differences are observed in circular dichroism spectra, relative fluorescence intensities, Km values, and carbohydrate composition. It is concluded that the two forms differ only in the structure of their (nonphosphorylated) carbohydrate side chains. In view of the possible interconversion of the two forms upon storage, caution must be observed in any attempt to attach clinical significance to the relative amounts of the two forms.

Dimeric nature and amino acid compositions of homogeneous canine prostatic human liver and rat liver acid phosphatase isoenzymes. Specificity and pH-dependence of the canine enzyme

Two isoenzymes of rat liver acid phosphatase (orthophosphoric-monoester phosphohydrolase (acid optimum) EC 3.1.3.2) have been purified to homogeneity, at least one of these for the first time. Both of the rat liver isoenzymes have identical specific activities towards p-nitrophenyl phosphate. Molecular weights of the native enzymes are 92 000 for rat liver isoenzyme I and 93 000 for isoenzyme II, while the subunit molecular weights are 51 000 and 52 000 respectively. Data on substrate specificity and pH dependence are presented for the homogeneous canine prostatic enzyme, which is also isolated as a dimeric enzyme of (native) molecular weight 89 000. Carbohydrate analysis data are presented for canine prostatic acid phosphatase and it is further noted that both isoenzymes of rat liver acid phosphatase are also glycoproteins. The amino acid compositions of the two rat liver isoenzymes are presented together with those of the similar dimeric acid phosphatase of human liver and of canine prostate. Comparison of these results with published data for the amino acid composition of human prostatic acid phosphatase shows substantial similarities. However, significant differences are seen in the amino acid composition of rat liver acid phosphatase isoenzyme I as compared to a previous literature report. Most notably, 17 histidine residues are found per mol of isoenzyme I and 18 for isoenzyme II.

The function of carbohydrate moiety and alteration of carbohydrate composition in human alkaline phosphatase isoenzymes

The relationship between the structure and function of alkaline phosphatase (orthoposphoric monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1) isoenzymes is under investigation in a number of laboratories. The present study deals with the effects of glycosidase digestion on the alkaline phosphatase isoenzymes. Changes in physicochemcial properties, activity, affinity for various lectins and blood group antisera, carbohydrate composition and biological half-life were investigated. The desialylated hepatic enzyme was shown to be more heat labile and more sensitive to protease digestion in the presence of 0.5% sodium dodecyl sulfate than native hepatic enzyme. Helix contents of the native and desialated hepatic enzyme were calculated to be 39.0 and 30.8%, respectively, and apparent molecular weights 175,000 and 167,000, respectively. Intestinal enzyme preparations treated with alpha-mannosidase, exo-N-acetyl-Dglucosaminidase and endo-N-acetyl-D-glucosaminidase-D displayed a decrease in enzyme activity. Among these, the alpha-mannosidase-treated enzyme activity was the most clearly reduction. The maximum activity of the alpha-mannosidase-treated intestinal enzyme was observed to change from 40 mM Mg2+ to 5--10 mM Mg2+.

Preparation of homogeneous human prostatic acid phosphatase using concanavalin A-sepharose 4-B

A simple, rapid and efficient procedure is presented for the purification of human prostatic acid phosphatase (orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.2) to homogeneity. The method employs two steps suitable for use with large quantities of material, followed by chromatography on concanavalin A-Sepharose as its sole column step. The procedure also permits the recovery of purified enzyme in higher yields than earlier methods.

Comparative studies on immobilization of human prostatic acid phosphatase

Acid phosphatase (othophosphoric monoester phosphohydrolase (acid optimum), EC 3.1.3.2) from the human prostate was immobilized by its protein moiety on cyanogen bromide-activated Sepharose, by carbohydrate moiety on Concanavalin-A-Sepharose, and by Schiff base formation with partially oxidized carbohydrate groups on ethylenediamine-Sepharose. The highest retention of enzyme activity, 80%, was found for the noncovalent immobilization on Concanavalin-A-Sepharose. It was demonstrated that the optimal pH changes for the Concanavalin-A-Sepharose and CNBr-Sepharose-enzyme complexes are electrostratic in character. In all cases of immobilization the enzyme has higher thermostability than that for the native enzyme under the same conditions. The effects of the enzyme stabilization were interpreted in terms of the multipoint interaction between the enzyme molecule and the carrier.