Multiple forms of alkaline phosphatases in human liver tissue

Towards improved genetic diagnosis of human differences of sex development

Despite being collectively among the most frequent congenital developmental conditions worldwide, differences of sex development (DSD) lack recognition and research funding. As a result, what constitutes optimal management remains uncertain. Identification of the individual conditions under the DSD umbrella is challenging and molecular genetic diagnosis is frequently not achieved, which has psychosocial and health-related repercussions for patients and their families. New genomic approaches have the potential to resolve this impasse through better detection of protein-coding variants and ascertainment of under-recognized aetiology, such as mosaic, structural, non-coding or epigenetic variants. Ultimately, it is hoped that better outcomes data, improved understanding of the molecular causes and greater public awareness will bring an end to the stigma often associated with DSD.

Expressiveness of Bone Markers in Breast Cancer with Bone Metastases

INTRODUCTION

On a global scale, the malignant growth of mammary gland is the most common type of cancer in women. In the progress of mammary carcinoma, osseous metastatic invasion has a pivotal significance because it is a frequent complication occurring at an early stage of the disease.

BACKGROUND

Bone metastases in breast cancer patients lead to increased mortality and decreased health-related quality of life. Therefore, early diagnostic assessment and treatment is requested. Meanwhile the progress of the disease should be monitored closely. Regarding health-related quality of life and lifetime prolongation, osseous metastases should be early diagnosed, therapied, and monitored. Up to date the gold standard is the whole-body scintigraphy. This kind of bone imaging features has high sensitivity but shows loss of specificity.

AIM

This study aims to investigate the diagnostic versatility of bone markers in its resorption and formation function to detect bone metastases in patients with breast cancer.

PATIENTS, MATERIALS, AND METHODS

For this purpose, the concentration of competing bone processing tumor markers in serums of 78 patients was detected and analyzed. Two groups of women with mammary carcinoma with and without osseous metastases were built to examine the presence (or absence) of statistically significant disparity of tumor marker concentration. The tumor markers employed in this study were the carboxyterminal collagen type I telopeptid (CTX), known as beta-crosslaps (β-CTx), the alkaline phosphatase (AP), and its isoenzymes (especially the bone-specific AP [B-AP]). Additionally, the tumor markers for breast cancer (CA 15-3 and CEA) were analyzed in both groups.

RESULTS

Our results provide evidence that in both groups, tumor markers such as β-CTx and B-AP were a promising tool for the detection and exclusion of bone metastases in breast cancer. This comprehensive investigation shows both β-CTx and B-AP are able to fulfill the conditions of a competent appliance to detect osseous metastases of patients with mammary carcinoma.

CONCLUSION

Concerning the urgency of early and frequent detection, staging, and disease monitoring of mammary carcinoma with osseous metastases, this study renewed and underlined the importance of biochemical tumor markers - especially β-CTx and B-AP - and laid a clinical-based cornerstone to build up on a prospective research.

The effect of pH, temperature and plaque thickness on the hydrolysis of monofluorophosphate in experimental dental plaque

Monofluorophosphate (MFP), an anti-caries agent commonly used in toothpaste, is known to be degraded to fluoride and orthophosphate by bacterial phosphatases in dental plaque. We have examined the effect of pH, temperature, plaque thickness and some ions on this process. Both natural plaque and artificial microcosm plaque incubated with purified MFP at pH 4-10 showed an optimum pH of approximately 8 for hydrolysis. Diffusion and concomitant hydrolysis were examined in an apparatus in which artificial plaque was held between rigid membranes separating two chambers. When MFP diffused through a plaque of 0.51-mm thickness over 4 h it was almost completely hydrolysed at pH 8, but hydrolysis on diffusion decreased as the pH deviated from 8. MFP in toothpaste extract showed a similar pH susceptibility to hydrolysis, according to the inherent pH of the toothpaste. Hydrolysis of MFP in the toothpaste was reduced by no more than 10% when compared with a matched-pH control, suggesting that other toothpaste ingredients had no major influence on hydrolysis. Transport was slower and hydrolysis at pH 6 more complete the thicker the plaque, but hydrolysis was not significantly slower at 23 degrees C than at 37 degrees C. The addition of various potential activating or inhibiting ions at 0.1 and 1.0 mmol/l had small and non-significant effects on hydrolysis. The results suggest that MFP toothpaste should be formulated and used to maximise enzymic hydrolysis of this complex anion, and that plaque pH control is probably the most important factor.

Intestinal alkaline phosphatase isoforms in rabbit tissues differ in glycosylation patterns

OBJECTIVES

In patients with advanced liver cirrhosis or chronic nephritis, an intestinal alkaline phosphatase (IAP)-like enzyme is ectopically expressed in the liver or kidney. In this study, we used rabbit organs as a human pathological model, because the rabbit liver or kidney expresses an IAP-like enzyme as the predominant isozyme, unlike humans.

METHODS

IAP and the IAP-like enzyme were purified from rabbit intestine and kidney, respectively, by immunoaffinity chromatography using a monoclonal antihuman IAP antibody. Some properties of the IAP and IAP-like enzyme expressed in rabbit organs are compared.

RESULTS

Some of their catalytic and physicochemical properties differed. In particular, the net charge, molecular mass, and hydrophobicity of IAP from rabbit intestine was slightly different from the IAP-like enzyme from rabbit kidney. There was a difference in the sugar chain structure between the two enzymes according to the results of lectin affinity chromatography, and part of the peptide maps differed slightly. However, there was no difference in the peptide maps after treatment with endo-N-acetylglucosaminidase F.

CONCLUSIONS

The primary structures of IAP and the IAP-like enzyme are basically similar, except for the glycosylation process of the respective AP isozymes.

Conidial alkaline phosphatase from Neurospora crassa

An alkaline phosphatase was purified from conidia of a Neurospora crassa wild type strain. The M(r) of the purified native enzyme was estimated as ca 145,000 and 110,000 by gel filtration, in the presence and absence of magnesium ions, respectively. A single polypeptide band of M(r) 36,000 was detected by SDS-PAGE, suggesting that the native enzyme was a tetramer of apparently identical subunits. Conidial alkaline phosphatase was an acidic protein (pl = 4.0 +/- 0.1), with 40% carbohydrate content. Optimal pH was affected by substrate concentration and magnesium ions. Low concentrations of calcium ions (0.1 mM) had slight stimulatory effects, but in excess (5 mM) caused protein aggregates with decreased activity. The enzyme specificity against different substrates was compared with those reported for constitutive or Pi-repressible alkaline phosphatases produced by N. crassa. The results suggested that the conidial alkaline phosphatase represented a different class among other such enzymes synthesized by this organism.

Liver-like alkaline phosphatase in the tissue-unspecific type enzyme found in rabbit organs

Rabbit liver and kidney tissues are known to produce an intestinal-like alkaline phosphatase (IAP-like enzyme) as a dominant isozyme, with a minor isozyme of tissue-unspecific type (UAP), unlike humans and other mammalians. We investigated immunohistochemically and biochemically these unique isozymes in the rabbit liver and bone, and compared them with the human isozyme. In rabbit liver, UAP was found to be localized only in the apical part of the membrane of cells lining the bile duct, whereas IAP-like enzyme was found in the sinusoidal membrane of hepatocytes. Rabbit liver UAP was separated from IAP-like enzyme by DEAE-cellulose column chromatography. Rabbit bone tissue contained only one UAP isozyme. The two UAPs were biochemically and physicochemically compared with human liver AP. Both UAPs reacted with an anti-human liver AP monoclonal antibody, not with an anti-human bone AP monoclonal antibody, indicating that both enzymes have the same antigenicity as human liver AP. Rabbit liver and bone UAPs had similar N-linked sugar-chain heterogeneities to the respective human enzymes. In addition, rabbit bone AP also had an O-linked sugar chain, as did human bone AP, unlike rabbit and human liver APs.

Alkaline phosphatase from rat osseous plates: purification and biochemical characterization of a soluble form

A soluble form of an alkaline phosphatase obtained from rat osseous plates was purified 204-fold with a yield of 24.3%. The purified enzyme showed a single protein band of Mr 80,000 on SDS-PAGE and an apparent molecular weight of 163,000 by gel filtration on Sephacryl S-300 suggesting a dimeric structure for the soluble enzyme. The specific activity of the enzyme at pH 9.4 in the presence of 2 mM MgCl2 was 19,027 U/mg and the hydrolysis of p-nitrophenyl phosphate (K0.5 = 92 microM) showed positive cooperativity (n = 1.5). The purified enzyme showed a broad substrate specificity, however, ATP, bis(p-nitrophenyl) phosphate and pyrophosphate were among the less hydrolyzed substrates assayed. Surprisingly the enzyme was not stimulated by cobalt and manganese ions, in contrast with a 20-25% stimulation observed for magnesium and calcium ions. Zinc ions exerted a strong inhibition on p-nitrophenylphosphatase activity of the enzyme. This paper provides a simple experimental procedure for the isolation of a soluble form of alkaline phosphatase which is induced by demineralized bone matrix during endochondral ossification.

Activation energy and lectin affinity chromatography of gamma-glutamyltransferase as a marker for enzyme heterogeneity

Lectin affinity chromatography of gamma-glutamyl transferase (GGT,EC 2.3.2.2) is able to detect differences in the carbohydrate moiety of the enzyme. Binding of tissue GGT towards lectins is significantly different from serum GGT, showing increased galactosylation in tissue forms. Kidney GGT is less glycosylated than GGT from other tissues (liver, pancreas, prostate, vesiculae seminales). Increases in sialic acid content of GGT are associated with an increase in the activation energy of the catalyzed reaction. Differences in galactose, fucose and N-acetylhexosamine content induce much smaller effects on activation energy. In liver diseases, serum GGT is characterized by an altered affinity against lectins recognizing galactose, fucose and N-acetyglucosamine and by increased activation energy. In patients with liver disease, use of fixed temperature conversion factors can lead to erroneous calculations of serum GGT enzyme activity (errors up to 13.3%).

Endoprotease in human liver transforming multiple forms of alkaline phosphatase

Two forms of alkaline phosphatase, extracted from human liver and named API1 and API3, are of high molecular mass, but API3 is the larger molecule and is membrane-bound while API1 is smaller and soluble. Enzyme kinetics are identical. It is suggested that API1 is produced from API3 by an endoprotease. We demonstrated the action of an endoprotease in human liver homogenate converting API3 into API1. In the absence of this enzyme no conversion occurred. This enzyme is active at an acidic pH (less than 6.5) in the presence of Ca.. or Mg.. -ions. It is inhibited by traces of EDTA. It is insensitive to diisopropyl fluoro-phosphate, to leupeptin and to reducing or oxidizing chemicals. At alkaline pH (8.6) its activity is rapidly destroyed. The enzyme is stable in acidic buffer. We conclude that API1 is indeed formed from API3 in the living cell by enzymatic conversion.

Clinical use of serum enzymes in liver disease

Some of the many enzymes found in hepatocytes can be measured in the serum and are used as tests of liver function. We now review the current knowledge of their physiology and pathophysiology and outline their clinical usefulness. We divide them into two categories: enzymes that primarily reflect cholestasis, such as the alkaline phosphatase, the 5'-nucleotidase, and the gamma-glutamyl transpeptidase, and those that primarily reflect hepatocellular necrosis, such as the aminotransferases. We also briefly discuss several enzymes of more limited usefulness.

Similarity of the sugar moiety of human alkaline phosphatases between the kidney cortex and duodenum, or medulla and ileum

Characteristics of human renal cortex and medulla alkaline phosphatase (ALP) were compared. Enzymatic and hydrophobic properties of both ALPs were almost similar. However, the results of concanavalin A affinity chromatography and wheat germ agglutinin affinity electrophoresis, exhibited that sugar chain structure(s) might be different between the cortex and medulla ALPs. In addition, the molecular mass and substrate specificity differed from each other, and these results of cortex and medulla ALPs were well accordant with those of human duodenal and ileal ALPs, respectively, as described previously (Clin Chim Acta 1987;163:279-287).

Isoelectric focusing on cellulose acetate membrane: a separation procedure for alkaline phosphatase isoenzymes

An isoelectric focusing technique for the separation of alkaline phosphatase isoenzymes on cellulose acetate membrane is described. Optimal conditions for isoelectric focusing were established by changing ampholine concentration and focusing conditions. Bone, liver, intestinal, and placental isoenzymes can be resolved into various sub-bands in a pH range of 4.1 to 5.2. These sub-bands were correlated with the findings of electrophoretic isoenzyme separation. The whole procedure proves very simple to perform and comparatively time saving (4 h). This procedure may help clarify the problems of ALP isoenzyme differentiation when electrophoretic patterns are unresolved.

Molecular nature of three liver alkaline phosphatases detected by drug administration in vivo: differences between soluble and membranous enzymes

1. Activities of alkaline phosphatase, liver-membranous, liver-soluble and serum-soluble, were dramatically induced in dogs by treatment with both phenobarbital and brovanexine. The treatment induced a 17-fold increase in membranous, a 155-fold increase in soluble, and a 105-fold increase in serum alkaline phosphatases. 2. There was no difference in the enzymatic behavior of the three forms of alkaline phosphatase, on heat stability, amino acid inhibition and optimum pH. 3. When the three alkaline phosphatases were treated initially with n-butanol, their apparent molecular size was identical. After treatment with phosphatidylinositol-specific phospholipase C, the liver-soluble and serum-soluble alkaline phosphatase were of the same molecular size. Liver-membranous alkaline phosphatase, however, was larger in molecular size than the other two forms, suggesting a difference between soluble and membranous alkaline phosphatase forms. 4. In terms of the sugar moiety of the three alkaline phosphatase forms, the membranous enzyme showed more of the higher affinity fraction and less of the lower affinity fraction of concanavalin A, compared with the soluble enzymes. 5. Consequently, it is possible that the membranous enzyme may be solubilized by an enzyme such as phosphatidylinositol-specific phospholipase C and modify further the sugar moiety of alkaline phosphatase molecules, resulting in serum alkaline phosphatase transfer from the soluble enzyme in liver.

The mechanism of elevated alkaline phosphatase activity after bile duct ligation in the rat

Alkaline phosphatase activity in the liver and intestine increases after bile duct ligation, reportedly by increased enzyme synthesis. To ascertain the mechanism of this increased synthesis in the absence of a cDNA clone encoding the enzyme, we have estimated the concentration of liver and intestinal alkaline phosphatase mRNA by translational analysis. Monospecific antiserum to rat placental alkaline phosphatase was raised. The resulting antiserum precipitated two peptides of 53 and 56 kd after translation of liver poly(A) + RNA. The precipitation of both peptides was blocked by the single 64 kd placental alkaline phosphatase. Processing of the cell-free products by microsomal membranes produced peptides of 62 and 64 kd. Antiserum to rat intestinal alkaline phosphatase also identified two peptides as products of intestinal RNA translation. After bile duct ligation, we confirmed a transient 2-fold increase in alkaline phosphatase activity in the intestine and a more constant 7-fold increase in the liver. However, the alkaline phosphatase mRNA concentration remained unchanged in both organs. We conclude that increased alkaline phosphatase synthesis after bile duct ligation results from an enhanced rate of translation of mRNA.

Hydrophobic properties of alkaline phosphatases

The butanol extraction method of Morton (1950), a routine step in enzyme purification, is discussed with special reference to a hydrophobic form of alkaline phosphatase from human liver tissue. This form slowly precipitates from butanol-extracted liver tissue homogenates stored at 4 degrees C. Furthermore, it is lost when acetone precipitation is applied as a purification procedure. The soluble form in liver tissue is shown to have a higher relative hydrophobicity than the serum liver/bone isoenzyme. The use of sodium cholate in the isolation of the hydrophobic form produces an artefact in isoelectric focusing, which can be abolished by dialysis prior to focusing.