The purification of inosine 5'-monophosphate dehydrogenase from Escherichia coli by affinity chromatography on immobilized Procion dyes

Biomimetic-dye affinity adsorbents for enzyme purification: application to the one-step purification of Candida boidinii formate dehydrogenase

Formate dehydrogenase (FDH, EC 1.2.1.2) was purified from Candida boidinii cells in a single step by biomimetic-dye affinity chromatography. For this purpose, seven' biomimetic analogues of the monochlorotriazine dye, Cibacron(R) Blue 3GA (CB3GA), and parent dichloro-triazine dye, Vilmafix Blue A-R (VBAR), bearing a car-boxylated structure as their terminal biomimetic moiety, were immobilized on crosslinked agarose gel, Ultrogel A6R. The corresponding new biomimetic-dye adsorbents, along with nonbiomimetic adsorbents bearing CB3GA and VBAR, were evaluated for their ability to purify FDH from extracts obtained after press-disintegration of C. boidinii cells. Optimal conditions for maximizing specific activity of FDH in starting extracts (1.8 U/mg) were realized when cell growth was performed on 4% methanol, and press disintegration proceeded in four consecutive passages before the homogenate was left to stand for 1 h (4 degrees C). When compared to nonbiomimetic adsorbents, biomimetic adsorbents exhibited higher purifying ability. Furthermore, one immobilized biomimetic dye, bearing as its terminal biomimetic moiety mercap-topyruvic acid linked on the chlorotriazine ring (BM6), displayed the highest purifying ability. Adsorption equilibrium data which were obtained for the BM6 adsorbent in a batch system corresponded well to the Langmuir isotherm and, in addition, breakthrough curves were taken for protein and FDH adsorption in a fixed bed of BM6 adsorbent. The dissociation constant ( K(D)) of the complex between immobilized BM6 and FDH was found to equal 0.05 microM. Adsorbent BM6 was employed in the purification of FDH from a 18-L culture of C. boidinii in a single step (60% overall yield of FDH). The purified FDH afforded a single-band on sodium dodecyl sulphate poly-acrylamide gel electrophoresis, and a specific activity of 7,0 U/mg (30 degrees C).

Dye-ligand affinity systems

Dye-ligands have been considered as one of the important alternatives to natural counterparts for specific affinity chromatography. Dye-ligands are able to bind most types of proteins, in some cases in a remarkably specific manner. They are commercially available, inexpensive, and can easily be immobilized, especially on matrices bearing hydroxyl groups. Although dyes are all synthetic in nature, they are still classified as affinity ligands because they interact with the active sites of many proteins mimicking the structure of the substrates, cofactors, or binding agents for those proteins. A number of textile dyes, known as reactive dyes, have been used for protein purification. Most of these reactive dyes consist of a chromophore (either azo dyes, anthraquinone, or phathalocyanine), linked to a reactive group (often a mono- or dichlorotriazine ring). The interaction between the dye ligand and proteins can be by complex combination of electrostatic, hydrophobic, hydrogen bonding. Selection of the supporting matrix is the first important consideration in dye-affinity systems. There are several methods for immobilization of dye molecules onto the support matrix, in which usually several intermediate steps are followed. Both the adsorption and elution steps should carefully be optimized/designed for a successful separation. Dye-affinity systems in the form of spherical sorbents or as affinity membranes have been used in protein separation.

Cyclodextrin biospecific-like displacement in dye-affinity chromatography

Interactions between Cibacron Blue F3GA (CB F3GA), as a model of triazine dye, and 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD), as a model of cyclodextrin, were investigated by monitoring the spectral shift that accompanies the binding phenomena. Matrix analysis of the difference spectral titration of CB F3GA with HP-beta-CD revealed only two absorbing species, indicating a host-guest ratio of 1:1. The dissociation constant for this HP-beta-CD-CB F3GA complex, Kd, was found to be 0.43 mM. The data for HP-beta-CD forming inclusion complexes with CB F3GA were used to develop the concept of competitive elution by inclusion complexes in dye-affinity chromatography. When this concept was applied to the elution of L-lactate dehydrogenase from a CB F3GA affinity matrix, it was shown to be an effective elution strategy. It provided a 15-fold purification factor with 89% recovery and sharp elution profile (0.8 column volumes for 80% recovery), which is as good as that obtained by specific elution with NADH (16-fold, 78% recovery and 1.8 column volumes). In addition, the new elution strategy showed a better purification factor and sharper elution profile than traditional non-specific elution with KCl (4.5-fold, and 1.4 column volumes). Hence, competitive elution by inclusion complexes may be a promising strategy for eluting proteins with high recoveries and purification factors in dye-affinity chromatography.

Cibacron blue F3G-A-attached uniform and macroporous poly(styrene-co-divinylbenzene) particles for specific albumin adsorption

Cibacron blue F3G-A-carrying uniform macroporous particles were proposed as an alternative sorbent for specific albumin adsorption. These particles were produced by a multistep polymerization procedure. In the first step of production, the uniform polystyrene seed particles were prepared by a dispersion polymerization method. Next. the polystyrene seed particles were first swollen by dibutylphthalate and then by styrene-divinylbenzene mixture in an aqueous emulsion medium. In the last step (i.e. repolymerization), styrene-divinylbenzene mixture was copolymerized within the swollen seed particles in the absence or presence of a stabilizer (e.g. poly(vinyl alcohol)). Although a considerable amount of non-specific BSA adsorption was observed on the surface of the particles produced in the absence of PVA, zero non-specific albumin adsorption could be achieved with the uniform macroporous particles produced in the presence of PVA. The stabilizer on the particle surface was also used as a ligand in the further derivatization of macroporous particles for specific albumin adsorption. Cibacron blue F3G-A was then covalently attached onto the surface of uniform macroporous particles. Specific albumin adsorption capacities up to 93 mg g(-1) could be achieved with the cibacron blue F3G-A-carrying macroporous particles of 6.25 microm in size.

Biomimetic dye affinity chromatography for the purification of bovine heart lactate dehydrogenase

Three biomimetic dye ligands bearing as a triazine-linked terminal moiety a carboxylated structure, which mimics substrates and inhibitors of L-lactate dehydrogenase (LDH), were immobilized on cross-linked agarose Ultrogel A6R. These biomimetic dyes are purpose-designed analogues of commercial monochlorotriazine Cibacron Blue 3GA (CB3GA) and parent dichlorotriazine Vilmafix Blue A-R (VBAR). The corresponding biomimetic adsorbents, along with non-biomimetic adsorbents bearing CB3GA and VBAR, were evaluated for their ability to purify LDH from bovine heart crude extract. When compared with non-biomimetic adsorbents, all biomimetic adsorbents exhibited a higher purifying ability. Further, one immobilized biomimetic dye, bearing mercaptopyruvic acid as biomimetic moiety, displayed the highest purifying ability. The concentration of immobilized dye affected both the capacity and the purifying ability of the affinity column, exhibiting an optimum value 2.2 mumol dye/g moist gel. This affinity adsorbent was exploited for the purification of LDH from bovine heart in a two-step procedure. The procedure consisted in a biomimetic dye affinity chromatography step (NAD+/sulphite elution, 25-fold purification, 64% step yield), followed by DEAE-agarose ion-exchange chromatography (1.4-fold purification, 78% step yield). The purified enzyme exhibited a specific activity of ca. 480 u/mg at 25 degrees C (content of impurities: pyruvate kinase and glutamic-oxaloacetic transaminase were not detected; malate dehydrogenase, 0.01%), compared with ca. 250 u/mg of commercial bovine heart LDH (malate dehydrogenase, 0.05%) suitable for analytical purposes.

Monosize microbeads based on polystyrene and their modified forms for some selected medical and biological applications

Polymeric particles are produced by different polymerization techniques. Phase inversion (dispersion) polymerization is one of the recent techniques to obtain monosize polymeric microbeads in the size range of 1-50 microns. The size and monodispersity of these microbeads can be adjusted by using several solvent systems (e.g., alcohol-water mixtures) with different polarities and by changing the type and amount of monomer, initiator and stabilizer. Surfaces of these microbeads can be further modified by different techniques including coating with different copolymers. Monosize polymeric microbeads are widely used in medical and biological applications as carriers, such as in immunoassays and cell separation, in site-specific drug delivery systems, in nuclear medicine for diagnostic imaging, in studying the phagocytic process, in affinity separation of biological entities, etc. Here, some important aspects of the production of monosize microbeads based on polystyrene and their modified forms are briefly discussed, and some selected medical and biological applications are summarized.

Engineering surface charge. 1. A method for detecting subunit exchange in Escherichia coli glutathione reductase

The gene gor encoding Escherichia coli glutathione reductase was mutated to create a positively charged N-terminal extension consisting of five arginine residues followed by a factor Xa cleavage site to the enzyme polypeptide chain. The modified protein assembled in vivo to yield a dimeric enzyme with kinetic parameters indistinguishable from those of wild-type glutathione reductase. The N-terminal extension could not be released by treatment with factor Xa but could be removed by exposure to trypsin, again without effect on the enzyme activity. The modified enzyme was readily separated from the wild-type enzyme by means of ion-exchange chromatography or nondenaturing polyacrylamide gel electrophoresis. Incubation of the modified and wild-type enzymes, separately or as a mixture, with NADH led to their partial inactivation, and activity was restored by exposure to 1 mM reduced glutathione. No hybrid dimer was formed in the mixture of modified and wild-type enzymes, as judged by polyacrylamide gel electrophoresis, strongly suggesting that the inactivation induced by NADH was not due to dissociation of the parental dimers. The addition of otherwise benign positively or negatively charged extensions to the N- or C-terminal regions of the constituent polypeptide chains of oligomeric enzymes offers a simple route to detecting hybrid formation and the causative subunit dissociation and exchange.

Engineering surface charge. 2. A method for purifying heterodimers of Escherichia coli glutathione reductase

Two gor genes encoding different mutants of Escherichia coli glutathione reductase have been expressed in the same E. coli cell, leading to the creation of a hybrid form of the enzyme dimer. One of the gor genes carried, in addition to various directed mutations, a 5' extension that encodes a benign penta-arginine "arm" added to the N-terminus of the glutathione reductase polypeptide chain [Deonarain, M.P., Scrutton, N.S., & Perham, R.N. (1992) Biochemistry (preceding paper in this issue)]. This made possible, by means of ion-exchange chromatography or nondenaturing polyacrylamide gel electrophoresis, the facile separation of the hybrid enzyme from the two parental forms. Moreover, the two subunits in the hybrid enzyme could be made to carry different mutations. In this way, glutathione reductases with only one active site per dimer were generated: the effects of replacing tyrosine-177 with glycine in the NADPH-binding site, which greatly diminishes the Km for glutathione and switches the kinetic mechanism from ping-pong to ordered sequential, and of replacing His-439 with glutamine in the glutathione-binding site, which greatly diminishes the Km for NADPH, were both found to be restricted to the one active site carrying the mutations. This system of generating separable enzyme hybrids is generally applicable and should make it possible now to undertake a more systematic study of catalytic mechanism and assembly for the many enzymes with quaternary structure.

Active site complementation in engineered heterodimers of Escherichia coli glutathione reductase created in vivo

By directed mutagenesis of the cloned Escherichia coli gor gene encoding the dimeric flavoprotein glutathione reductase, Cys-47 (a cysteine residue forming an essential charge-transfer complex with enzyme-bound FAD) was converted to serine (C47S) and His-439 (required to facilitate protonation of the reduced glutathione) was converted to glutamine (H439Q). Both mutant genes were placed in the same plasmid, pHD, where each of them came under the control of a strong tac promoter. This was designed to achieve equal over-expression of both genes in the same E. coli cell. The parental homo-dimers show no (C47S) or very little (H439Q) activity as glutathione reductases. The formation in vivo of heterodimers, carrying one crippled and one fully functional active site, was detected by absorbance spectroscopy and fluorescence emission spectrometry of enzyme-bound FAD and by active site complementation. The fractional distribution of homo- and hetero-dimers was in accord with that expected for a random association of enzyme subunits. In a homo-dimer, the H439Q mutation leads to a big fall in the value of Km for NADPH which binds some 1.8 nm from the point of mutation (Berry, A., Scrutton, N.S. & Perham, R. N. Biochemistry 28, 1264-1269 (1989)). However, the one active site in the H439Q/C47S hetero-dimer exhibited kinetic parameters similar to those of the wild-type enzyme. Thus, the effect of the H439Q mutation must be retained within the active site that accommodates it and is not transmitted through the protein to the second active site across the subunit interface.(ABSTRACT TRUNCATED AT 250 WORDS)

Directed mutagenesis of the redox-active disulphide bridge in glutathione reductase from Escherichia coli

Directed mutagenesis of the gor gene from Escherichia coli encoding the flavoprotein glutathione reductase was used to convert the two cysteine residues that comprise its redox-active disulphide bridge to alanine (C42A) and serine (C47S) residues. A double mutant (C42AH439A) was also created in which His-439, the proton donor/acceptor in the glutathione-binding site, was additionally converted into an alanine residue. The C42A and C47S mutants were both unable to catalyse the reduction of glutathione by NADPH. The C42A mutant retained the transhydrogenase activity of the wild-type enzyme, whereas the C47S mutant was also inhibited in this reaction. These results support the view that in the catalytic mechanism of E. coli glutathione reductase, the thiolate form of Cys-42 acts as a nucleophile to initiate disulphide exchange with enzyme-bound glutathione and that the thiolate form of Cys-47 generates an essential charge-transfer complex with enzyme-bound FAD. Titration of the C42A and C42AH439A mutants indicated that the imidazole side-chain of His-439 lowered the pKa of the charge-transfer thiol (Cys-47) from 7.7 to 5.7, enhancing its ability to act as an anion at neutral pH. Several important differences between these mutants of E. coli glutathione reductase and similar mutants (or chemically modified forms) of other members of the flavoprotein disulphide oxidoreductase family were noted, but these could be explained in terms of the different redox chemistries of the enzymes concerned.

Design and applications of biomimetic anthraquinone dyes. III. Anthraquinone-immobilised C.I. reactive blue 2 analogues and their interaction with horse liver alcohol dehydrogenase and other adenine nucleotide-binding proteins

C.I. Reactive Blue 2 analogues were bonded onto an agarose support matrix by a novel method which entailed immobilisation by the anthraquinone ring 1-amino group as opposed to the usual triazine ring coupling methods. Dyes with spacer arms attached to the anthraquinone ring 1-amino group were synthesised by reacting methoxytriazine analogues of C.I. Reactive Blue 2 with chloroacetyl chloride and ethylenediamine. Unlike the blue parent dyes, all C.I. Reactive Blue 2 analogues with derivatised anthraquinone ring 1-amino groups were of a characteristic red colour. This change of chromaticity was entirely expected since the anthraquinone ring 1-amino group is an important component of the C.I. Reactive Blue 2 chromophore. Chromatographic studies indicated that, in comparison to adsorbents comprising triazine ring-immobilised dyes, adsorbents formed from C.I. Reactive Blue 2 analogues immobilised by the anthraquinone ring were better suited to the isolation of horse liver alcohol dehydrogenase and other adenine nucleotide-requiring enzymes. Similarities between C.I. Reactive Blue 2 analogues immobilised by the anthraquinone ring and N6-(6-aminohexyl)adenine nucleotide derivatives could be identified which may account for these observations. These studies confirm that highly effective affinity ligands based on synthetic textile dyes can be designed in a rational manner.

The applications of reactive dyes in enzyme and protein downstream processing

Downstream processing of proteins is often a key factor in the overall process of satisfying product specifications and meeting current commercial demands. In this context, affinity chromatography and other techniques based on the affinity concept have revolutionized protein purification technology, although they have failed to demonstrate their broader applicability at the process scale. On the other hand, reactive dyes offer many advantages as pseudoaffinity media and in many occasions have successfully circumvented problems associated with conventional affinity ligands. The main features of reactive dyes include their broad spectrum of interaction with proteins, low cost, ready availability, high reactivity, ease of immobilization, and both biological and chemical stability. Consequently, dye-ligand media now find application in both analytical and process-scale purification of proteins by techniques such as low- and high-pressure performance affinity chromatography, affinity partitioning, and affinity precipitation.

Inhibition of inosine monophosphate dehydrogenase by sesquiterpene lactones

Inosine monophosphate (IMP) dehydrogenase had previously been determined to be a likely target enzyme for the sesquiterpene lactones, a class of potential anti-neoplastic drugs. IMP dehydrogenase was purified approx. 770-fold from the P-388 lymphocytic leukemia tumor cell line. The Km values for the substrates, IMP and NAD, were determined to be 12 microM and 25 microM, respectively. Xanthine monophosphate (XMP) was shown to be a competitive inhibitor with a Ki of 67 microM. Mycophenolic acid gave mixed-type inhibition with a Ki of 8 nM for the noncompetitive component and a Ki of 2 nM for the competitive component. Dissociation constants (Kd) and rate constants for inhibition of IMP dehydrogenase by nine different sesquiterpene lactones were determined. The highest Kd was seen with 2,3-dihydrohelenalin while the lowest Kd was observed with bis-helenalinyl malonate. Binding of the drugs by IMP dehydrogenase increased as the size of the drug increased. Also, changes in structure at position 6 had a relatively large effect on the Kd. There was no correlation with hydrophobicity, as determined by octanol/water partition. The first-order rate constants for the reaction of the sesquiterpene lactones with IMP dehydrogenase (k1) and the second-order rate constants for the reaction of the sesquiterpene lactones with glutathione (k2) were also determined. The rate constants for most of the sesquiterpene lactones with the alpha-methylene-gamma-lactone moiety were similar and were approximately twice as great as the rate constants for those sesquiterpene lactones with only the alpha, beta-unsaturated cyclopentenone ring. Microlenin had approximately 5-times the reactivity of the other sesquiterpene lactones towards IMP dehydrogenase, but had approximately the same reactivity towards glutathione, suggesting that it was bound to the enzyme in a way which facilitated its reaction with one or more essential sulfhydryls. The same procedure was used for a series of N-substituted maleimide compounds with the N-substituent ranging in size from a methyl group to a benzyl group. The binding of the maleimide compounds was generally tighter than for the sesquiterpene lactones and there was an increase in binding with size.

Purification and characterization of glutathione reductase encoded by a cloned and over-expressed gene in Escherichia coli

An expression vector, pKGR, for the gor gene from Escherichia coli encoding glutathione reductase was constructed by subcloning of an AvaII fragment of the Clarke & Carbon bank plasmid pGR [Greer & Perham (1986) Biochemistry 25, 2736-2742] into the plasmid pKK223-3. The expression of glutathione reductase from the plasmid pKGR was found to have been successfully placed under the control of the tac promoter. Transformation of E. coli cells with this plasmid resulted in 100-200-fold increase in glutathione reductase activity in cell-free extracts. A rapid purification procedure for the enzyme, based on affinity chromatography on Procion Red HE-7B-CL-Sepharose 4B, was developed. The purified enzyme was homogeneous as judged by SDS/polyacrylamide-gel electrophoresis, and all its properties were consistent with the DNA sequence of the gene [Greer & Perham (1986) Biochemistry 25, 2736-2742] and with those previously reported for E. coli glutathione reductase [Mata, Pinto & Lopez-Barea (1984) Z. Naturforsch. C. Biosci. 39, 908-915]. These experiments have enabled an investigation of the protein chemical and mechanistic properties of the enzyme by site-directed mutagenesis.

Design and application of bio-mimetic dyes in biotechnology

The last decade or so has been the introduction of multi-coloured reactive dyes as substitutes for natural biological ligands in the purification of proteins by affinity chromatography. This paper reviews the evidence for the remarkable selectivity of the interaction of reactive dyes with proteins and describes our recent work with dye analogues. Terminal ring, bridging ring and anthraquinone ring analogues of Cibacron Blue F3G-A were synthesised de novo and shown to interact selectively with the NAD+-binding site of horse liver alcohol dehydrogenase but with affinities differing by several orders of magnitude. It is anticipated that these novel dye ligands will lead to affinity adsorbents with improved affinity, capacity and specificity.

Isolation and properties of an H2O-forming NADH oxidase from Streptococcus faecalis

An H2O-forming NADH oxidase from Streptococcus faecalis, recently described [Hoskins, D. D., Whiteley, H. R. and Mackler, B. (1962) J. Biol. Chem. 237, 2647-2651], has been isolated as a uniform protein with specific activity 690 U/mg in a total yield of 50% by a two-step affinity chromatography procedure. The enzyme is metal-free and has a molecular mass of about 51 000 Da and probably consists of a single polypeptide chain. As shown by fluorimetric titration, the prosthetic group is 1 mol FAD/mol protein. The affinity behaviour of the enzyme gives evidence for the existence of a dinucleotide-binding domain capable of binding NADH or FAD. The enzyme is specific for NADH (Km = 4.1 X 10(-5) M), NADPH is not oxidized. O2 is the preferred electron acceptor, in addition FAD and, very slowly, one-electron acceptors are reduced. It is not clear whether the reduction of FAD proceeds through the dinucleotide-binding site or by exchange of the prosthetic group. The stoichiometry of the reaction with O2 corresponds to the consumption of 2 mol NADH/mol O2, and only H2O is formed (2 NADH + 2 H+ + O2----2 NAD+ + 2 H2O). Neither H2O2 nor O2.- is detected as intermediate and H2O2 cannot replace O2 as an oxidant. The enzyme can, mainly in its reduced state, be inhibited by -SH reagents. Spectral data give no evidence for the existence of radical intermediates during reduction. The enzyme can obviously accept more than two electrons/mol. On the basis of these data two possible reaction mechanisms are discussed. A proposal for the biological purpose of the reaction is made.

Specific inhibition of L-type pyruvate kinase by the triazine dye Procion Blue MX-R

Incubation of the triazine dye Procion Blue MX-R with L- and M-type pyruvate kinase resulted in rapid time- and dye-concentration-dependent loss of activity. L-type pyruvate kinase was protected only by a low concentration of Mg2+; this was not the case with the M-type enzyme. Modification of the L-type form resulted in the incorporation of 1.54 +/- 0.057 mol of dye/mol of enzyme subunit in the absence of Mg2+, but only 0.73 +/- 0.024 mol of dye/mol of enzyme subunit in the presence of Mg2+. Tryptic peptide mapping of L-type pyruvate kinase modified in the presence and in the absence of Mg2+ further indicated that there were two sites modified in the enzyme, one of which was protected by Mg2+. The pKa of the nucleophile involved in the modification was calculated to be 7.1, implicating the possible involvement of a histidine residue. L-type enzyme was bound to Sepharose-immobilized Procion Blue MX-R specifically in the presence of Mg2+, whereas binding of the M-type enzyme was Mg2+-independent. The specific interaction of L-type pyruvate kinase with the dye was exploited in the large-scale purification of the enzyme and in the isolation of the phosphorylated enzyme.

Isolation and characterization of glyoxylate dehydrogenase from the fungus Sclerotium rolfsii

Glyoxylate dehydrogenase (glyoxylate:NAD+ oxidoreductase) was purified 600-fold in three steps from crude extracts of the fungus Sclerotium rolfsii (Corticium rolfsii Curzi). Two of the purification steps involved dye-affinity chromatography. The enzyme is a tetramer of Mr 250 000, with identical subunits of Mr 57 000. Inhibition studies suggest that there is one essential thiol group per active site.

Dye-ligand affinity chromatography: the interaction of Cibacron Blue F3GA with proteins and enzymes

The dye Cibacron Blue F3GA has a high affinity for many proteins and enzymes. It has therefore been attached to various solid supports such as Sephadex, Sepharose, polyacrylamide, and the like. In the immobilized form the dye has rapidly been exploited as an affinity chromatographic medium to separate and purify a variety of proteins including dehydrogenases, kinases, serum albumin, interferons, several plasma proteins, and a host of other proteins. Such a diversity shown by the blue dye in binding several unrelated classes of proteins has generated considerable work in terms of studies of the chromophore itself and also the immobilized ligand. As a prelude to realizing the full potential of the immobilized Cibacron Blue F3GA, an understanding of the basic interactions of the dye with its surroundings must be gained. It has been recognized that the dye is capable of hydrophobic and/or electrostatic interactions at the instance of the ambient conditions. The study of interactions of the dye with salts, solvents, and other small molecules indicates the nature of the interactions of the dye with different kinds of groups at the interacting sites of proteins. The review will cover such interactions of the dye with the proteins, the interactions of the proteins with the immobilized ligand, and the media used to elute the bound protein in several cases, and thus consolidate the available information on such studies into a cogent and comprehensive explanation.

Metal ion-promoted binding of proteins to immobilized triazine dye affinity adsorbents

Low concentrations of metal ions, particularly those of the first row transition series such as Zn2+, Co2+, Mn2+, Ni2+, Cu2+, and, to a lesser extent, the group IIA ions, Ca2+ and Mg2+, promotes binding of carboxypeptidase G2, alkaline phosphatase and yeast hexokinase to immobilized Procion Red H-8BN, Procion Yellow H-A and Cibacron Blue F3G-A respectively. The binding of ovalbumin to immobilized Cibacron Blue F3G-A and Procion Orange MX-G is selectively enhanced in the presence of AI3+. With ovalbumin and alkaline phosphatase, the effect is almost totally specific for both the metal ion and dye, whereas with carboxypeptidase G2 and hexokinase, metal ions such as Co2+, Ni2+, Mn2+, Cu2+, Ca2+ and Mg2+ also promote binding to varying degrees. Almost all other monovalent and trivalent metal ions appear to be ineffective. Metal ion-bound enzymes can subsequently be eluted with appropriate chelating agents of the amine, aminocarboxylate or substituted pyridine classes.

The interaction of yeast hexokinase with Procion Green H-4G

1. A number of reactive triazine dyes specifically and irreversibly inactive yeast hexokinase at pH 8.5 and 33 degrees C. Under these conditions, the enzyme is readily inactivated by 100 microM-Procion Green H-4G, Blue H-B, Turquoise H-7G and Turquoise H-A, is less readily inactivated by Procion Brown H-2G. Green HE-4BD, Red HE-3B and Yellow H-5G and is not inactivated at all by Procion Yellow H-A. 2. The inactivation of hexokinase by Procion Green H-4G is competitively inhibited by the adenine nucleotides ATP and ADP and the sugar substrates D-glucose, D-mannose and D-fructose but not by nonsubstrates such as D-arabinose and D-galactose. 3. Quantitatively inhibited hexokinase contains approx. 1 mol of dye per mol of monomer of mol.wt. 51000. The inhibition is irreversible and activity cannot be recovered on incubation with high concentration (20 mM) of ATP or D-glucose. 4. Mg2+ protects the enzyme against inactivation by Procion Green H-4G but enhances the rate of inactivation by all the other Procion dyes tested. In the presence of 10 mM-Mg2+ the apparent dissociation constant between enzyme and dye is reduced from 199.0 microM to 41.6 microM. Binding of the dye to hexokinase is accompanied by characteristic spectral changes in the range 560-700 nm. 5. Mg2+ promotes binding of yeast hexokinase to agarose-immobilized Procion Green H-4G but not to the other dyes tested. Elution could be effected by omission of Mg2+ from the column irrigants or by inclusion of MgATP or D-glucose, but not by D-galactose. These effects can be exploited to purify hexokinase from crude yeast extracts. 6. The specific active-site-directed binding of triazine dyes to yeast hexokinase is interpreted in terms of the crystallographic structure of the hexokinase monomer.

Affinity chromatography on immobilised triazine dyes. Studies on the interaction with multinucleotide-dependent enzymes

A systematic investigation into the interaction of several triazinyl dyes with two enzymes from purine metabolism, IMP dehydrogenase (IMP: NAD+ oxidoreductase, EC 1.2.1.14( and adenylosuccinate synthetase (IMP: L-aspartate ligase (GDP-forming), EC 6.3.4.4) has been conducted. Evidence from kinetic inhibition studies, enzyme inactivation with specific affinity labels and specific elution techniques from agarose-immobilised dyes indicate that triazine dyes such as Procion Blue H-B (Cibacron Blue F3G-A), Red HE-3B and Red H-3B are able to differentiate between the nucleotide-binding sites of these enzymes. This information has been exploited to design specific elution techniques for the purification of these enzymes by affinity chromatography.