Alkaline phosphatase (EC 3.1.3.1) from pig kidney brush-border membranes was solubilized from membrane precipitates by butan-1-ol at a critical pH of 7.0. The 12000-fold purification procedure included (NH(4))(2)SO(4) precipitation, DEAE-and TEAE-cellulose chromatography, Sephadex G-200 gel filtration and neuraminidase digestion followed by DEAE-cellulose chromatography. The purified protein contained 20% (w/w) carbohydrate and had mol.wt. 150000-156000 as estimated by Sephadex filtration and ultracentrifuge analysis. It was a tetrameric glycoprotein consisting of identical subunits, and it had a molecular activity at 25 degrees C of 2600s(-1) per tetramer. Its concentration in kidney was estimated to be 8.5-8.8mg/kg.
The enzymic properties of alkaline phosphatase (EC 3.1.3.1) from pig kidney brush-border membranes were studied. 1. It hydrolyses ortho- and pyro-phosphate esters, the rate limiting step (V(max.)) being independent of the substrate. It transphosphorylates to Tris at concentrations above 0.1m-Tris. 2. The pH optimum for hydrolysis was between 9.8 and 10. The pK of the enzyme-substrate complex is 8.7 for p-nitrophenyl phosphate and beta-glycerophosphate. Excess of substrate inhibits the enzymic activity with decreasing pH. The pK of the substrate-inhibited enzyme-substrate complex, 8.7, is very similar to that for the enzyme-substrate complex. The pK values of the free enzyme appear to be 8.7 and 7.9. 3. Inactivation studies suggest that there is an essential tyrosine residue at the active centre of the enzyme. 4. The energy of activation (E) and the heat of activation (DeltaH) at pH9.5 showed a transition at 24.8 degrees C that was unaffected by Mg(2+). 5. Kinetic and atomic-absorption analysis indicated the essential role of two Zn(2+) ions/tetrameric enzyme for an ordered association of the monomers. Zn(2+) in excess and other bivalent ions compete for a second site with Mg(2+). Mg(2+) enhances only the rate-limiting step of substrate hydrolysis. 6. Amino acid inhibition studies classified the pig kidney enzyme as an intermediate type of previously described alkaline phosphatases. It has more similarity with the enzyme from liver and bone than with that from placenta.
The selective fluorescence staining of two fungi, Candida albicans and Blastomyces dermatitides, with Uvitex 2B and Calcofluor White M2R was studied in deparaffinized and frozen sections of mouse kidney and lung. Both fluorochromes emitted maximally at about 430 nm, independent of the mounting media (Kaiser's gelatin or Entellan). In addition to fungi, both fluorochromes also stained elastic fibres. The fluorescence intensity remained unchanged after storage of sections for more than 6 months in conventional slide boxes. The two fluorochromes showed the following differences: Calcofluor faded 1.25 times faster than Uvitex when illuminated with ultraviolet light. Calcofluor showed a greater affinity for tissues in general, and red cells and renal tubular casts in particular. Counterstaining of deparaffinized sections with Hemalum and Eosin reduced the fungi fluorescence and suppressed the general background fluorescence. However, it led to an intensification of Eosin staining and the fluorescence of red cells in Calcofluor-stained sections but not in Uvitex-stained ones. Similarly, the background fluorescence in frozen sections was reduced by Evans Blue, although elastic fibres still fluoresced after staining with Calcofluor. The degree of staining selectivity, and thus the contrast produced within a histological specimen, was greater with Uvitex 2B than with Calcofluor White M2R.
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