Chromatographic purification of a mammalian histidine decarboxylase on charged and non-charged alkyl derivatives of agarose

Interactions between model membranes and lignin-related compounds studied by immobilized liposome chromatography

In order to elucidate the modes of interaction between lignin precursors and membranes, we have studied the influence of temperature, lipid composition and buffer composition on the partitioning of monolignol and dilignol model substances into phospholipid bilayers. The partitioning was determined by immobilized liposome chromatography, which is an established method for studies of pharmaceutical drugs but a new approach in studies of lignin synthesis. The temperature dependence of the retention and the effect of a high ammonium sulfate concentration in the mobile phase demonstrated that the interaction involved both hydrophobic effects and polar interactions. There was also a good correlation between the partitioning and the estimated hydrophobicity, in terms of octanol/water partitioning. The partitioning behavior of the model substances suggests that passive diffusion over the cell membrane is a possible transport route for lignin precursors. This conclusion is strengthened by comparison of the present results with the partitioning of pharmaceutical drugs that are known to pass cell membranes by diffusion.

Histidine decarboxylase in human basophilic leukemia (KU-812-F) cells. Characterization and induction by phorbol myristate acetate

The human leukemic cell line KU-812-F is known to differentiate into mature basophil-like cells under serum-free culture conditions. In the present study, the activity of histidine decarboxylase (HDC), a histamine-forming enzyme, in KU-812-F cells was found to be high, ranging from 10 to 57 pmol/min/mg protein. The great variation in HDC activity appeared to be due to different percentages and degrees of maturity of basophil-like cells during differentiation of this cell line. The enzyme was inhibited by alpha-fluoromethylhistidine but not by carbidopa, was unable to form dopamine from L-3,4-dihydroxyphenylalanine, and had a Km value for histidine of 0.27 mM, indicating that it was HDC and not aromatic amino acid decarboxylase. The HDC activity increased 1.8-fold when the cells were stimulated by phorbol myristate acetate, which is known to activate protein kinase C, and this increase was blocked by staurosporine, a potent inhibitor of protein kinase C.

High-performance liquid chromatography of proteins on compressed, non-porous agarose beads. II. Anion-exchange chromatography

Macroporous agarose beads were rendered impermeable to proteins by shrinkage and cross-linking in organic solvents. The chromatographic properties of compressed beds of these non-porous beads derivatized for high-performance ion-exchange chromatography were studied, e.g., the resolution as a function of gradient time, flow-rate (at constant gradient volume) and loading capacity. The columns permit high flow-rates and the resolution is about the same at low and high flow-rates. The beads are stable up to pH 14.

Wide-pore silica-based ether-bonded phases for separation of proteins by high-performance hydrophobic-interaction and size-exclusion chromatography

This paper examines the use of wide-pore silica-based hydrophilic ether-bonded phases for the chromatographic separation of proteins under mild elution conditions. In particular, ether phases of the following structure identical to Si-(CH2)3-O-(CH2-CH2-O)n-R, where n = 1, 2, 3 and R = methyl, ethyl or n-butyl, have been prepared. These phases can be employed either in high-performance hydrophobic-interaction or size-exclusion chromatography, depending on mobile phase conditions. In the hydrophobic-interaction mode, a gradient of decreasing salt concentration, e.g., from 3 M ammonium sulfate (pH 6.0, 25 degrees C), yields sharp peaks with high mass recovery of active proteins. In this mode, retention can be controlled by salt type and concentration, as well as by column temperature. In the size-exclusion mode, use of medium ionic strength, e.g., 0.5 M ammonium acetate (pH 6.0) yields linear calibration of log (MW[eta]) vs. retention volume. Even at 0.05 M salt concentration, no stationary phase charge effects on protein elution are observed. These bonded-phase columns exhibit good column-to-column reproducibility and constant retention for at least five months of continual use. Examples of the high-performance separation of proteins in both modes are illustrated.

Mammalian histidine decarboxylase; changes in molecular properties induced by oxidation and reduction

Histidine decarboxylase from a murine mastocytoma has been submitted to different separation methods. In these experiments the activity peaks were often very broad. This heterogeneity of the enzyme is traced back to the formation of aggregates, differing in apparent molecular weight by a multiple of about 55,000, as a result of oxidation. Under non-oxidative conditions the histidine decarboxylase activity is confined to one peak in both molecular sieve chromatography, hydrophic interaction chromatography, chromatography on hydroxy apatite, pore gradient electrophoresis and electrofocusing. The molecular weight of the enzyme is estimated to be 110,000 by pore gradient electrophoresis (alkylated enzyme). The isoelectric point is pH 4.9--5.0, determined by electrofocusing under reducing conditions.

Mammalian histidine decarboxylase. Stability studies with special reference to the effect of salts

Histidine decarboxylase (EC 4.1.1.22) prepared from a murine mastocytoma is activated up to six-fold when the concentration of phosphate in the assay medium is increased from 1 mM to 150 mM. Chloride and sulfate, on the other hand, are inhibitory and appear to interfere with the binding of pyridoxal phosphate to the enzyme. The inhibition by chloride is relatively less pronounced at high than at low concentrations of phosphate. The enzyme is inhibited by heavy metal ions and to some extent by alkylation and oxidation, but also by strong reduction. The histidine decarboxylase activity is stablized by 150 mM potassium phosphate, 1 mM dithiothreitol and 10 micrometers pyridoxal phosphate when stored at 6--8 degrees C. This holds true for both crude extract enzyme and enzyme purified by molecular sieving and hydrophobic interaction chromatography.

Peptide inhibition of mammalian histidine decarboxylase

The hypothesis that N-terminal histidine peptides might act as inhibitors to histidine decarboxylase was investigated. A murine mastocytoma was utilized as enzyme source. The crude extract of this tissue exhibits high rates of decarboxylation of both histidine and DOPA and was used to establish the specificity in the effect of the compounds tested. For kinetic analyses a highly purified histidine decarboxylase fraction was used. The effect of some representative peptides on both enzyme activities were recorded. Histidine decarboxylase exclusively was inhibited by N-terminal histidine peptides. None of the other peptides investigated interfered negatively with this enzyme. This inhibition was consistent in the purified preparation and appeared to be more pronounced with increasing hydrophobicity in the second amino acid. Histidyl-phenylalanine was found to be about 100-fold as potent as the commonly used specific histidine decarboxylase inhibitor alpha-methyl histidine. It is concluded that small peptides with histidine as the N-terminal amino acid might act as specific inhibitors for mammalian histidine decarboxylase. An analog effect of small tyrosyl or phenylalanyl peptides was not seen for the DOPA decarboxylase.

[Purification and detection of multiple forms of histidine decarboxylase in rat gastric mucosa (author's transl)]

A specific histidine decarboxylase from rat gastric mucosa has been obtained at high purity and good yield (purification about 600-fold). The purification procedure included double (NH4)2SO4 fractionation, ion-exchange chromatography, preparative isoelectric focusing in a granulated gel and gel filtration. Only the specific histidine enzyme was obtained by that procedure; DOPA decarboxylase, a non-specific enzyme, was absent in our final preparation. Each step of the purification was visualized by polyacrylamide gel electrophoresis and analytical isoelectric focusing. The purified enzyme was apparently homogenous by criteria of electrophoresis and gel filtration and has a molecular weight of 94 000. Several protein bands appeared after isoelectric focusing and the enzyme activity was localized in 3 distinct peaks. The gastric enzyme consists of 3 active forms which could be distinguished by their isoelectric points: 5.4, 5.75 and 6. Moleculare weights estimated by SDS polyacrylamide gel electrophoresis were 97 000, 93 000 and 90 000, and no subunits were observed. Pyridoxal phosphate was required as a coenzyme and resolution of the holoenzyme agreed with a portion of the coenzyme tightly bound to the apoenzyme. The purified enzyme was stable at low ionic strength, near neutral pH; concentrated reducing agents inhibit the enzyme.

Hydrophobic interaction chromatography on uncharged Sepharose derivatives. Effects of neutral salts on the adsorption of proteins

In the presence of different neutral salts in high concentrations (ionic strength 1-3 M), pentyl-Sepharose was saturated with human serum albumin, and decyl-Sepharose with ovalbumin and phycoerythrin; the amount of protein bound to the adsorbent was taken as a measure of the hydrophobic interaction. The effects of the different ions on the adsorption of protein could, with one exception, be arranged according to the Hofmeister series. As the adsorption might also be influenced by alterations in the protein conformation, caused by the neutral salts, the proteins were studied by circular dichroism. Circular-dichroism spectra showed that 3 M sodium bromide and 3 M sodium thiocyanate changed the conformation of human serum albumin and ovalbumin, whereas 3 M sodium chloride and 1 M sodium sulphate did not. The conformational changes observed with sodium bromide and thiocyanate were accompanied by decreasing protein-adsorbent interaction, except for ovalbumin in 3 M sodium thiocyanate.

The major sialoglycoprotein of the human erythrocyte membrane. Release with a non-ionic detergent and purification

The major sialoglycoprotein of the human erythrocyte membrane has been selectively released by the non-ionic detergent Tween 20 and further purified in detergent-free buffers by hydroxyapatite chromatography and, finally, by hydrophobic interaction chromatography on pentyl-Sepharose. The purified glycoprotein shows one main zone, PAS-1, and up to three minor zones after staining both for protein and carbohydrate in polyacrylamide gel electrophoresis in the presence of dodecyl sulfate. The relative staining intensities are concentration dependent. When the purified glycoprotein has been heated to 100 degrees C in dodecyl sulfate, more stain appears in the most rapid zone, PAS-2, and less in the slower zones, indicating a disaggregation of oligomeric forms of this glycoprotein, including a dimer, PAS-1.