Comparison of a tumour-derived form of intestinal alkaline phosphatase with foetal and adult intestinal alkaline phosphatases

An unusual alkaline phosphatase isoenzyme associated with gastric carcinoma

We describe a 50-year-old man with a diagnosis of gastric carcinoma made on gastroscopy after X-rays of the thoracolumbar spine had revealed multiple lytic metastases. A bone marrow aspirate showed adenocarcinoma cells. Polyacrylamide gel electrophoresis incorporating wheat germ lectin was used to separate the serum alkaline phosphatase isoenzymes. Isoenzyme separation showed a markedly increased amount of bone isoenzyme, a normal amount of liver isoenzyme and a considerable amount of an intestinal-like isoenzyme running cathodic to the bone isoenzyme. There was also some immunoglobulin-complexed alkaline phosphatase, which, when digested, showed more of the intestinal-like isoenzyme. This was a variant alkaline phosphatase isoenzyme found in a patient with a gastric carcinoma with a super bone scan. There have been two previous reports of patients with a variant alkaline phosphatase isoenzyme and a super bone-scan.

Intestinal type alkaline phosphatase hyperphosphatasemia associated with liver cirrhosis

Hyperphosphatasemia due to increased intestinal type serum alkaline phosphatase was noted in a 48-year-old male who had asymptomatic liver cirrhosis. The alkaline phosphatase activity in the serum was 828 U/l (our reference range in adults: 57-194 U/l), 94% of which was of the intestinal type as measured by an immunoprecipitation method. The intestinal component of alkaline phosphatase was separated into two major and some minor components using electrophoresis and isoelectrofocusing. One of the major components had similar mobility to that of a standard intestinal enzyme purified from adult intestine. The components were heat-labile and neuraminidase-resistant. Serial lectin affinity chromatography, however, indicated that sugar chain compositions of the alkaline phosphatase were different from those of the standard tissue intestinal enzyme. These results and further enzymological studies suggest that the patient's serum alkaline phosphatase basically consisted of several intestine-like isoforms.

Human fetal intestinal alkaline phosphatase: molecular heterogeneity and immunological detection in amniotic fluids

Human fetal intestinal alkaline phosphatase (fIALP) is present in amniotic fluids as free dimers (Mr 140,000) or membrane-bound through phosphatidylinositol residues. Extraction of corresponding particulate material with Triton X-100, resulted in release of tetrameric high Mr fIALP forms (Mr 380,000). In individual amniotic fluids, as well as in meconeum, both dimeric and tetrameric fIALP are sialylated to various extents. When measured by a double sandwich-ELISA, up to 10-fold higher fIALP antigen levels were found in amniotic fluids than when determined by an enzyme antigen immunoassay, based upon fIALP enzyme activity measurements. Frequency analysis of fIALP antigen levels, showed a more symmetrical distribution than analysis of fIALP enzyme activities; likewise, the lower 95% confidence limit, calculated for the fIALP antigen distribution curve, overlapped less with the bulk of values. In cystic fibrosis amniotic fluids, measurements of fIALP antigen levels resulted in a lower false-negativity outcome than fIALP enzyme activity measurements, whereas in amniotic fluids of trisomy pregnancies fIALP enzyme activities and fIALP antigen levels were equally unpredictive.

The human alkaline phosphatases: what we know and what we don't know

A review of the human alkaline phosphatases dealing specifically with (1) the gene loci, (2) characterization and discrimination of the various enzymes, (3) polymorphism at the enzyme level, (4) cDNA and gene structures, (5) membrane binding, (6) the carbohydrate moieties, (7) hypophosphatasia, (8) alkaline phosphatases in malignancies, (9) function.

Lectin affinity electrophoresis of alkaline phosphatase for the differentiation of bone and hepatobiliary disease

An affinity electrophoresis procedure is described for the separation and quantification of the bone- and liver-derived fractions of alkaline phosphatase in plasma. Separation is carried out on cellulose acetate membrane pre-soaked with buffer containing wheat germ lectin. The electrophoretic mobility of the bone enzyme is preferentially retarded by the lectin and this fraction is well separated from the liver fraction. After separation, enzyme activity is demonstrated by staining using an indigogenic alkaline phosphatase substrate incorporated in agar gel, and the stained fractions quantified by densitometry. The procedure has low imprecision, good linearity, and the activities of the bone and liver fractions correlate well with values obtained using nonelectrophoretic quantification methods. The procedure is especially suitable for use in the diagnostic laboratory.

Effect of bromelain on alkaline phosphatases of intestinal and non-intestinal tissues and serum

Human alkaline phosphatases extracted with butanol from liver, kidney and placenta, and from foetal and adult small intestine each contain fragments with molecular masses within the range of approximately 8 kDa to 20 kDa which can be removed by digestion with bromelain. However, in the case of adult intestine, this fragment (which is presumed to represent a membrane-binding domain) can only be demonstrated in tissue extracted immediately after removal at operation. Similar fragments are also present in foetal intestinal phosphatase in amniotic fluid, and in liver and bone alkaline phosphatases recovered from serum. Again, however, adult intestinal phosphatase from serum differs in the absence of the bromelain-sensitive fragment. These observations indicate differences in the ways in which intestinal and non-intestinal alkaline phosphatases gain access to the circulation, and also have implications for structural studies on intestinal phosphatase extracted post mortem from adult tissue.

Diagnostic aspects of alkaline phosphatase and its isoenzymes

The changes in serum alkaline phosphatase that are of main diagnostic importance result from increased entry of enzyme into the circulation. This results from increased osteoblastic activity in bone disease, and increased synthesis of alkaline phosphatase by hepatocytes in hepatobiliary disease. The liver and bone forms of alkaline phosphatase are differently-glycosylated forms of a single gene product. The main value of their specific estimation is found in patients in whom bone and liver diseases co-exist, for example, as a result of cancer. Abnormal expression of genetically-distinct alkaline phosphatase isoenzymes is valuable in monitoring cancers, particularly germ-cell tumors. These isoenzymes include Regan and Nagao isoenzymes, which correspond respectively to normal placental and placental-like alkaline phosphatases, and the Kasahara isoenzyme which appears to result from re-expression of a fetal intestinal alkaline phosphatase gene.

The physical characteristics and enzymatic modification of fetal intestinal alkaline phosphatase in amniotic fluid

The predominant form of alkaline phosphatase in amniotic fluid at 16 to 18 weeks gestation has the inhibition characteristics of the isoenzymes from adult and fetal small intestine. These characteristics are shared by an alkaline phosphatase of presumed intestinal origin occasionally found in the sera of premature neonates. However, in contrast to the rapid anodal migration of the latter enzyme, amniotic fluid phosphatase is of low electrophoretic mobility in polyacrylamide gel, and it has a high molecular weight. Digestion of amniotic fluid with bromelain produces a rapidly-migrating active enzyme form, with a molecular weight of about 135,000, compared with 145,000 for the fetal intestinal phosphatase in serum. The bromelain-treated amniotic fluid phosphatase is similar in size to a Kasahara isoenzyme in the serum of a cancer patient, which is itself thought to result from re-expression of a fetal intestinal phosphatase gene.