[Bacterial formate dehydrogenase. Substrate specificity and kinetic mechanism of S-formyl glutathione oxidation]

The substrate specificity of NAD-dependent formate dehydrogenase from the methylotrophic bacterium Achromobacter parvulus T1 was studied. The kinetic mechanism of S-formyl glutathione oxidation was determined. The initial velocity studies and inhibition analysis were carried out. It was shown that the kinetic mechanism for the enzyme with S-formyl glutathione as a substrate is similar to that with formate and is rapid-equilibrium random. Using independent methods, it was found that formate dehydrogenase forms a binary complex with S-formyl glutathione (Kd = 2.5 mM).

[Chemical modification of the lysine residues of bacterial formate dehydrogenase]

Inactivation of formate dehydrogenase by formaldehyde, pyridoxal and pyridoxal phosphate was studied. The effects of concentrations of the modifying agents, substrates, products and inhibitors on the extent of the enzyme inactivation were examined. A complete formate dehydrogenase inactivation by pyridoxal, pyridoxal, phosphate and formaldehyde is achieved by the blocking of 2, 5 and 13 lysine residues per enzyme subunit, respectively. The coenzymes do not protect formate dehydrogenase against inactivation. In the case of modification by pyridoxal and pyridoxal phosphate a complete maintenance of the enzyme activity and specific protection of one lysine residue per enzyme subunit is observed during formation of a binary formate-enzyme complex, or a ternary enzyme--NAD--azide complex. One lysine residue is supposed to be located at the formate-binding site of the formate dehydrogenase active center.

[The Homogeneous immunocofactor method of determining insulin]

An immunocofactor quantitative method of measuring insulin in solution was developed. The method uses antibody competitive binding of free and NAD labeled insulin. The NAD-insulin conjugate was obtained by covalent binding of the C(6)-aminogroup modified cofactor with insulin by means of soluble carbodiimide. To determine the NAD-insulin conjugate, which was not bound with antibodies, in the presence of antibodies and free insulin, an enzymic system of the cofactor regeneration with conjugated substrates of horse liver alcohol dehydrogenase, cyclohexanol and p-nitroso-N,N-dimethyl aniline, was employed. The sensitivity of insulin assay was about 5.10(-7) M.

Chemical modification of lysine residues in bacterial formate dehydrogenase

Specific modification of 4.4 lysine residues per molecule of formate dehydrogenase, from the methylotrophic bacterium Achromobacter parvulus I by pyridoxal, results in complete inactivation of the enzyme. The concentration effect of the modifying agent and substrates on the inactivation of formate dehydrogenase has been studied. Coenzymes do not protect the enzyme from inactivation. Complete maintenance of enzyme activity was achieved in the presence of saturating concentrations of the formate and upon formation of the ternary complex, enzyme-NAD-azide. Formate specifically protects two lysine residues per dimer molecule of the enzyme from modification. The presence of one essential lysine residue in the substrate-binding region of the enzyme active site is assumed.

[Kinetics of NAD-dependent formate dehydrogenase from the methanol-utilizing yeast Candida methylica]

A kinetic analysis of the mechanism of action of NAD-dependent formate dehydrogenase (EC 1.2.1.2) from the methanol-utilizing yeast Candida methylica has been carried out. The dependence of the initial reaction rate on substrate concentrations and the inhibition by the reaction products and substrate analogs were investigated. The data obtained suggest that the kinetics of the formate dehydrogenase action are consistent with the formation of a ternary enzyme--substrate complex. NAD is the first substrate and NADH is the last product of the reaction, respectively.

[Comparison of luciferase activity of homogenates from fireflies of different species]

The stability and catalytic properties of enzymes from fireflies of three species - Lucida mingrelica, Lucida mongolica and Lampris sp.-were investigated. The enzyme of the homogenate from Lampris sp. was found most stable. The enzyme specific activities of the three species differed greatly. The specific activity of the homogenate from Luciola mingrelica was 7 times higher than that from Lampris sp. The Km constants with respect to Mo ATP and luciferine were identified for each enzyme.

[Isolation and properties of NAD-dependent formate dehydrogenase from the yeast Candida methylica]

NAD-dependent formate dehydrogenase was purified from a cell-free extract of methanol-consuming yeast Candida methylica, using chromatography on DEAE-cellulose and gel-filtration on Sephadex G-200. The enzyme is electrophoretically homogeneous, consists of two identical subunits with molecular weight of 46,000 and is active within the pH range of 6-9; the Km values for NAD and formate are 1 . 10(-4) and 1,3 . 10(-2) M, respectively. Formate dehydrogenase is inhibited by p-chloromercurybenzoate, iodoacetate, dithionitrobenzoate and azide.

Study of the role of arginine residues in bacterial formate dehydrogenase

Modification of 12 arginine residues per molecule of formate dehydrogenase (formate : NAD+ oxidoreductase, EC 1.2.1.2.) from the methylotrophic bacterium, Achromobacter parvulus I, by 2,3-butanedione results in complete inactivation of the enzyme. Inactivation of the enzyme is reversible and proceeds in two steps via formation of the intermediate enzyme-butanedione complex. Coenzymes but not formate effectively protect formate dehydrogenase from inactivation. Complete maintenance of enzyme activity and specific protection of one arginine residue per enzyme subunit are achieved on formation of the binary complex, enzyme-NAD, or the ternary complex, enzyme-NAD-azide. One arginine residue is supposed to be located at the NAD-binding site of the formate dehydrogenase active centre.

[ATP-insulin conjugates and their use for immunofactor analysis]

A method resulting in ATP-insulin conjugates by covalent binding of ATP modified at C(6) amino group of the adenine residue with insulin was developed. The modified ATP was bound to insulin by means of metha-p-toluene sulfonate-N-cyclohezyl Nf [2-morpholinyl(4)ethyl]-carbodiimide. The ATP analogs and ATP-insulin conjugates possess the coenzyme activity in a reaction of luciferin oxidation by luciferase from the fireflies Luciola mingrelica. the catalytic properties of soluble and immobilize on CNBR-activated. Sepharose enzymes in reactions with native ATR, its modified derivatives and ATP--insulin conjugates were compared. The bioluminescence reaction involving ATP--insulin conjugate is inhibited by antibodies against insulin. This effect can form a basis for insulin detection in solution, which is based on competitive binding of free and antibody-labelled ATP--insulin conjugates.

[Kinetics of the NADH regenerating system using bacterial formate dehydrogenase]

The main kinetic regularities of the NADH regeneration system functioning was studied. A theoretical interpretation of the dependence of the stationary reaction rate in a two-enzyme system with a common cofactor on the enzyme, cofactor and substrate concentrations and the catalytic parameters of individual enzymatic processes was obtained. A mathematical analysis of the dependences of the stationary rate on the content of each enzyme in the system at different activity ratios of each enzyme and within a broad range of initial cofactor concentrations was carried out. The kinetics of regeneration of native NADH and the NADH immobilized on a water-soluble 4-vinylpyridine and acroleine copolymer in a model two-enzyme formate dehydrogenase--NADH dehydrogenase system were investigated.

[Role of sulfhydryl groups in the inactivation mechanism of bacterial formate dehydrogenase]

Inactivation of formate dehydrogenase (EC 1.2.1.2) from gramnegative methanol-utilizing bacteria was studied. It was shown that the thermal inactivation of the enzyme occurs at temperatures above 50 degrees; at temperatures below 40 degrees the inactivation is due to metal ion-catalyzed oxidation of its sulfhydryl groups. A possible general mechanism of the enzyme inactivation is proposed.

[Inhibition of glucose isomerase from Actinomyces olivocinereus 154 by polyols]

The inhibitory action of polyols, e. g. D-mannitol, D-glucitol, ribitol and xylitol, on the activity of glucose isomerase prepared from Actinomyces olivocinereus 154 was studied. All the polyols under study are purely reversible competitive inhibitors. The values of Ki for D-mannitol, D-sorbitol, D-arabitol, D-glucitol, ribitol and xylitol are 0.200, 0.140, 0.030, 0.024 and 0.020 M, respectively. The inhibition is to some extent decreased by increasing concentrations of the substrate and is completely abolished by increasing concentrations of Mg2+ and Co2+--up to 5.10(-2) and 5.10(-3) M, respectively.

[Conversion of D-glucose into D-fructose in a column reactor with immobilized glucose isomerase]

Conversion of D-glucose into D-fructose in a column reactor of a continuous type was studied using an immobilized enzyme, glucose isomerase from Actinomyces olivocinereus. The effective parameters of Km, Vmax, energy activation at various flow rates were calculated. During 32 days of continuous operation the enzyme activity fell down to 84% of the initial level. A system of recirculation was employed to use immobilized glucose isomerase with a low activity.

[Role of amino acid arginine residues of bacterial formate dehydrogenase]

Inactivation of NAD-dependent formate dehydrogenase by butandione-2,3 has been studied. The inactivation is shown to be due to specific modification of the arginine residues. The enzyme activity is completely abolished by modification of 17 arginine residues per enzyme molecule. Native formate dehydrogenase contains 50 arginine residues. The dependences of the enzyme inactivation rate on butandione and substrate concentrations and the pH profile of the inactivation have been investigated. Coenzymes (but not formate) protect the enzyme against inactivation. The enzyme activity is completely retained upon formation of a binary E-NAD complex and a ternary E-NAD-azide complex. Protection of one arginine residue per enzyme subunit is observed under formation of a ternary enzyme--inhibitor complex. The fole of the arginine residue in coenzyme binding is discussed.

[Immobilization of nicotine amide adenine dinucleotide derivatives and their function as cofactors of bacterial formic dehydrogenase]

NAD+ was modified with respect to the C(6)-amino group of the adenine residue by iod acetic acid alkylation in N1-position and subsequent rearrangement into N6-position. By condensation of N6-carboxy methyl-NAD+ with 1,6-diamino hexane, N6-[(6-aminohexyl)-acetamide]-NAD+ was synthesized. This process was controlled spectrophotometrically and by analytical isotachophoresis. NAD+ derivatives were found to maintain high co-enzymic activity in the reaction of formic oxidation with formic dehydrogenase from gram-negative methylotrophic bacteria, str. 1. Kinetic parameters of the reaction involving the resultant components were determined. NAD+N6-derivatives were covalently bound with the water insoluble carrier--Sepharose 4B and water soluble carriers--acrolein and 4-vinyl pyridine copolymers and dextran. The rates of formic dehydrogenase reduction of the native and immobilized cofactors were compared.

NAD-dependent formate dehydrogenase from methylotrophic bacterium, strain 1. Purification and characterization

1. NAD-dependent formate dehydrogenase was isolated from gram-negative methylotrophic bacteria, strain 1, grown on methanol. The purification procedure involved ammonium sulfate fractionation, ion-exchange chromatography and preparative isotachophoresis or gel filtration; it resulted in a yield of 40%. 2. The final enzyme preparations were homogeneous as judged by sedimentation in an ultracentrifuge. Formate dehydrogenase purified in the presence of EDTA reveals two bands on electrophoresis in polyacrylamide gel both after protein and activity staining. Two components are transformed into a single one after prolonged storage in the presence of 2-mercaptoethanol. 3. Formate dehydrogenase is a dimer composed of identical or very similar subunits. The molecular weight of the enzyme is about 80 000. 4. Amino acid composition and some other physico-chemical properties of the enzyme were studied. 5. Formate dehydrogenase is specific for formate and NAD as electron acceptor. The Michaelis constant was 0.11 mM for NAD and 15 mM for formate (pH 7.0, 37 degrees C). 6. Formate dehydrogenase was rapidly inactivated in the absence of -SH compounds. The enzyme retained full activity upon storage at ambient temperature in solution for half a year in the presence of 2-mercaptoethanol or EDTA.

[Investigation of essential SH-groups of bacterial formate dehydrogenase]

Modification of two SH-groups in the molecule of formate dehydrogenase by dithiobisnitrobenzoate or to dacetamide results in the enzyme inactivation. Coenzymes, but not the substrate, protect the enzyme against the inactivation. NAD in the presence of potassium azide completely preserves the enzyme activity. Two SH-groups per enzyme molecule are protected from modification. The Km values for partially inactivated formate dehydrogenase remain constant for both substrates. The enzyme with modified SH-groups does not bind conezymes. The pH-dependence of the inactivation rate reveals the ionizable group with pK 9.6 (25 degrees C). The involvement of essential SH-groups in coenzyme binding is discussed.

[Interaction between immobilized antibodies and the antigen-enzyme complex]

The interaction between immobilized antibodies against human immunoglobulin G (IgG) and the immunoenzyme complex IgG-peroxidase (IgG-P) was studied. The complex was obtained by covalent binding of IgG to peroxidase modified by sodium periodate. Study of the IgG-P binding kinetics and dissociation of the antibody-(IgG-P) complex showed that the antibodies immobilized on Sepharose reversibly interacted with IgG-P, similar to the antigen-antibody reaction in solution. The efficient values of the binding constants for the antibodies binding to Sepharose covalently and through the antigen-antibody bond are (2,2+/-0,5) 10(8) M-1 and (4,2+/-0,2) 10(8) M-1, respectively. The nature of a carrier and the immobilization method used do not significantly affect the rate of the complex binding to the antibodies. The activation energy of the reaction of IgG-P binding to the antibodies immobilized on Sepharose covalently and through the antigen-antibody bond is 7,3 and 4,1 kcal/mole, respectively. A procedure of titration of immobilized antibodies active sites with the antigen-enzyme complex is discussed.

[Quantitative determination of immunoglobulin A in human serum by an immunoenzyme technic]

A complex of immunoglobulin A (IgA) with peroxidase was obtained as a result of interaction of IgA with the enzyme, modified with sodium periodate. The molar ratio of IgA/peroxidase was equal to 1 in the complex, as shown by gelfiltration and sedimentation analysis. Peroxidase maintained 75% of the initial activity in the complex. The antigenic and enzymatic properties of the complex were retained completely within 5 months, if the preparation was kept at 4 degrees in phosphate buffer, pH 7.4. The complex isolated was used for quantitative estimation of IgA in human blood serum. The method is based on the reaction of competitive binding between free and labelled with peroxidase IgA molecules and antibodies, immobilized on inorganic porous carrier--sylochome. The method enables to estimate quantitatively IgA concentration within the limits of 102=105 ng/ml.

[Glucose-isomerizing enzyme from Actinomyces olivocinereus and its immobilization on aminosilochrome]

Glucose-isomerizing enzyme was isolated from the culture of Actinomyces olivocinereus. It was purified by the chromatography on DEAE-cellulose. The samples of glucose-isomerasing enzyme are homogeneous according to the results of analytical electrophoresis and ultracentrifugation. Glucose-isomerase is more stable than soluble one. The pH-optima of soluble and immobilized enzymes are 8.5 and 7.5, respectively. The temperature optimum of immobilized enzyme, Km, V, and activation energy do not change during immobilization. The immobilized sample has 58% activity of soluble enzyme.