Placental alkaline phosphatase

Alkaline phosphatase assays based on 3-glycerophosphate now appears to be obsolete, and methods buffered by either glycine or barbital are also obsolete as these buffers inhibit ALP or are poor buffers. Serum alkaline phosphatase is known to be composed of several isoenzymes which presumably arise from bone, liver, intestine, and placenta. The placental alkaline phosphatase is known to be much more resistant to heat denaturation than the other isoenzymes, and this resistance provides a simple test for it (5). The other enzymes can be separated through the differential inhibition by phenylalanine, by electrophoresis and by specific antibodies. However, the clinical usefulness of the results obtained is in doubt (23). 

Jemmerson, R., and Agre, M. (1987) Monoclonal antibodies to different epitopes on a cellsurface enzyme, human placental alkaline phosphatase, effect different patterns of labeling with protein A-colloidal gold. J. Histochem. Cytochem. 35, 1277-1284. 

Germ cell tumors Chorionic gonadotropin, alpha-fetoprotein, placental lactogen, placental alkaline phosphatase... 

Amino Acid Composition of Human Placental Alkaline Phosphatase... 

Human Placental Alkaline Phosphatase Relative Reaction Rates and Michaelis Constants for Various Substrates0... 

Self, C. H. (1985) Enzyme amplification—a general method applied to provide an immunoassisted assay for placental alkaline phosphatase. J. Immunol. Methods 76, 389-393. 

Makiya, R. and T. Stigbrand. 1992. Placental alkaline phosphatase is related to human IgG internalization in FIEp2 cells. Biochem. Biophys. Res. Commun. 182 624-630. 

Berger J, Hauber J, Hauber R, Geiger R, Cullen BR (1988), Secreted placental alkaline phosphatase a powerful new quantitative indicator of gene expression in eukaryotic cells, Gene 66 1-10. 

Chloramphenicol Acetyl Transferase, Secreted Placental Alkaline Phosphatase, P-Galactosidase... 

Apodaca G, Mostov KE. Transcytosis of placental alkaline phosphatase-polymeric immunoglobulin receptor hision proteins is regLilated by mutations of Ser664. J Biol Chem 1993 268 23712-9. 

Komoda, T., Koyama, I., Nagata, A., Sakagishi, Y., DeSchryver-Kecske-meti, K., Alpers, D.H. Ontogenic and phylogenic studies of intestinal, hepatic, and placental alkaline phosphatases. Gastroenterology 1986 91 277-286... 

COS cells have been used for the production of recombinant proteins, including HSV-1 glycoprotein B, ricin B chain, placental alkaline phosphatase, thrombomodulin, CD7, von Willebrand factor, human dihydropteridine reductase, human P-glucuronidase, interleukin 5 and human interferon-... 

Placental alkaline phosphatase (FLAP) is for monitoring of seminomas in nonsmokers only. 

Procedure for Serum, Intestinal, and Placental Alkaline Phosphatases—Substrate Phenyl Phosphate... 

A degree of organ specificity for substrate is to be expected. Thus, a substrate preference known is the ability of intestinal alkaline phosphatase to hydrolyze o-carboxyphenylphosphate more rapidly than other substrates (Fll, F13). Further, placental alkaline phosphatase is stated to hydrolyze p-nitrophenyl phosphate less rapidly than j8-glycerophos-phate (SI). Although ethanolamine phosphate is hydrolyzed preferentially by rat liver alkaline phosphatase, such a preference was missing from human liver preparations (Fll). 

Fia. 7. pH optima for intestinal and placental alkaline phosphatases (R) values in the absence of phenylalanine (D) in the presence of 0.005Af n-phenylalanine, and (L) in the presence of 0.005 Af L-phenylalanine. The substrate concentration was 0.018 Af phenyl phosphate. The triangles represent the intestine, and the circles represent human placenta. 

These are listed in Table 7. Just as in the case of substrate, organ-specific pH optima have been observed. Thus, for example, purified human placental alkaline phosphatase exhibits an optimum pH of 10.6 in contrast to 9.8 for the human intestinal preparation (Fig. 7). 

Certain kinetic features of L-phenylalanine inhibition will now be described for the purified human intestinal and placental preparations of alkaline phosphatase. In experiments on the effect of pH, Ghosh and Fishman (G5) observed that the degree of stereospecific L-phenylalanine inhibition of alkaline phosphatase from rat or human intestine and from human placenta is highly pH-dependent. Rat or human intestinal alkaline phosphatase exhibited maximum inhibition at pH 9.2 with phenyl phosphate as substrate, whereas the human placental alkaline phosphatase had a peak at pH 9.6 (Fig. 10). 

Fig. 10. Inhibition by L-phenylalanine as a function of pH. Triangles represent human intestinal and circles represent human placental alkaline phosphatase...

Fig. 17. Starch-gel patterns of Sephadex G-200 gel filtrates of human placental alkaline phosphatase showing the fractionation of variants A and B. The fraction numbers are indicated. The direction of migration was from bottom to top (anode).

In this laboratory, attempts (G6, G8) have been made to purify and crystallize human placental alkaline phosphatase enzyme by a number of procedures involving homogenization with 0.05 M Tris buffer (pH 8.6), extraction with butanol, ammonium sulfate precipitation, exposure to heat, ammonium sulfate fractionation, dialysis, repeated ethanol fractionation, gel filtration with Sephadex G-200 (Fig. 18), continuous curtain electrophoresis on paper (Beckman Model CP), multiple TEAE-cellulose anion exchange chromatography, and equilibrium dialysis. Variant A (electrophoretically fast-moving) of human placental alkaline... 

Pio. 18. Starch-gel pattern of placental alkaline phosphatase isozymes in the final steps of the purification (a) variant A and B in the best alcohol fractions before Sephadex-gel filtration, (b) variant A after removing B in the Sephadex-gel column, and (c) crystalline alkaline phosphatase (variant B). 

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