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J Bozal

Publications and source records attributed to J Bozal.

At least 55 records · Page 3Linked to original sources
PubMed1981

[Purine catabolism in rat brain (author's transl)].

In soluble rat brain fraction, the specific activities of purine nucleoside phosphorylase, guanine deaminase, 5'Nucleotidase and adenosine deaminase, decrease in their mentioned order. A kinetic parameter comparison between these enzymes shows that 5'Nucleotidase with AMP has the lowest KM and the greatest Vmax values, while purine nucleoside phosphorylase has its lowest KM and its greatest Vmax values with guanosine and with inosine, respectively. The enzymes activity is not modified by the metabolic intermediates differently from their own reaction products which behave as competitive inhibitors.

5'-Nucleotidase↗
PubMed1980

[alpha-n-benzoylarginine-2-naphthylamide-amidohydrolase activity in chicken liver (author's transl)].

The enzyme activity from chicken liver that hydrolizes alpha-N-benzoil-DL-arginine-2-naphthylamide (BANA) has been separated into three active fractions by chromatography on Sephadex G-100 and DEAE-cellulose. The enzyme in Fraction FEA has a molecular weight greater than or equal to 100,000. The other two enzymes in Fractions FE1B and FE2B have a molecular weight around 23,000 and are separated by DEAE-cellulose chromatography. The BANA-hydrolase of fraction FE2B is unstable at pH alkaline and activates trypsinogen, in contrast with the enzyme of fraction FEB1. Both are thiol enzymes which behave analogously against activators (cysteine, dithiotreitol and 2-mercaptoethanol) and inhibitors (PCMB, IAA, N-ethylmaleimide, Cu2+, Hg2+ and Zn2+).

Aminopeptidases↗
PubMed1980

[Acid proteinase of chicken liver. Purification and properties (author's transl)].

A method for purifying the haemoglobinolitic activity to acid pH in chicken liver is described. The purified preparation contains cathespin D activity since it is inhibited by diazoacetyl-DL-norleucine methylester in the presence of cupric ions, while thiol-enzyme reagents do not affect it. The molecular weight of the enzyme is approximately 40,000--45,000 and the pH optimum against haemoglobin and bovine serum albumin is 3.5-3.7. The rate of degradation of albumin and casein is much less than that of haemoglobin. Cathepsin D preparations with different purification degrees, exhibit a similar percentage of activation at acid pH; the highest activation is observed at pH 3.1-3.3.

Animals↗
PubMed1980

[Acid proteases from chicken liver. Cooperative hydrolysis of proteins (author's transl)].

Purified preparations of cathepsin D, BANA-hydrolase activity and dipeptidil aminopeptidase I from chicken liver, show a cooperative effect in the protein hydrolysis (acid-denatured haemoglobin and bovine serum albumin and native bovine serum albumin) at pH 5.0. The nature of the protein substrates determines their sensitivity to enzymatic digestion. The action of cathepsin D on proteins, in contrast which the BANA-hydrolase activity, releases polypeptides with high molecular weight, with scant--NH2 groups which can be valued by the ninhydrin method. These peptide fragments can then be further degraded by the protease BANA-hydrolase and the dipeptidil aminopeptidase I which is not active towards intact proteins.

Animals↗
PubMed1980

[Purification and properties of dipeptidyl amino-peptidase I from chicken liver (author's transl)].

Dipeptidyl aminopeptidase I (E.S. 3.4.14.1) from chicken liver was purified by the following steps: homogenization at pH 5, thermic precipitation, acetone fractionation and Sephadex G-100, DEAE-cellulose and organomercurial-Sepharose column fractionations. The purified enzyme appears to be homogeneous by polyacrylamide gel electrophoresis at both pH 4.5 and 8.3 and has an isoelectric point of 5.7 +/- 0.05. The molecular weight of the enzyme reale 167,000 +/- 17,000 on the Sephadex G-150 column chromatography. The optimum pH for hydrolysis of Gly-Phe-p-nitroanilide (GPNA) and Gly-Phe-B-naphthylamide was 5.8. The value of Km for the hydrolysis of GPNA was estimated at 3.3 mM. The enzyme required halide ions for activity and was activated by thiol reagents (dithiothreitol, cysteine and 2-mercaptoethanol). Accordingly, DAP I was inhibited by thiol-blocking reagents (PCMB, IAA, Hg2+). The enzyme oxidation with oxygen current was fostered by chloride anion (50 nM); nevertheless the activity was recovered when cysteine was present in the incubation mixture; the latter, besides, seems to perform as enzyme protector.

Animals↗
PubMed1979

Effect of salts on D-glycerate dehydrogenase kinetic behavior.

Bovine liver D-glycerate dehydrogenase (D-glycerate:NAD (NADP) oxidoreductase, EC 1.1.1.29) adapts its kinetic behaviour to a sequential mechanism. The presence of NaCl causes an appreciable variation in the Km and V values. relative to the both substrates in the hydroxypyruvate/D-glycerate dehydrogenase/NADH system, which does not happen in the D-glycerate/D-glycerate dehydrogenase/NAD system. The former system is inhibited by high concentrations of NaCl and activated by low salt concentrations. The hydroxypyruvate concentration causing substrate inhibition increases as the concentration of NaCl increases; excess NADH inhibition is independent of the salt concentration. The variation of the initial rates of both systems, in the presence of chlorides having monovalent and divalent cations, or sodium halides, Na2SO4 and NaNO3 (at constant ionic strength) suggests that the anions have a specific action on the enzyme. An increase in the NaCl concentration causes a displacement of the optimum D-glycerate dehydrogenase pH (with hydroxypyruvate and NADH as substrates) towards the acid area. The enzyme stability, at varying pH, varies with the salt concentration.

Animals↗
PubMed1979

[Kinetic mechanism of chicken liver mitochondrial malatedehydrogenase (author's transl)].

Kinetic mechanism of chicken liver mitochondrial malatedehydrogenase is established from the initial reaction rates and reaction product inhibition. The results obtained in the reduction of NAD+ (pH 10) allow the formulation of an ordered bi-bi mechanism in which the coenzyme is the first substrate added to the enzyme. Inhibition by the reaction products and by the excess of the very substrates, reveals the formation of the E-oxaloacetate; E-L-malate; E-NAD+-oxaloacetate; E.NAD+-NADH; E-NADH-NADH and E-NAD-NAD+ abortive complexes, the significance of which may be checked under defined experimental conditions. Enzyme inhibition by ATP, ADP and AMP in the reduction of NAD+ (pH10), accords with the proposed mechanism and proceeds via formation of the E-nucleotide and E-NAD+-nucleotide inactive complexes.

Animals↗
PubMed1979

[Comparative study of chicken liver xanthine dehydrogenase and bovine liver xanthine oxidase. dehydrogenase activity of xanthine oxidase (author's transl)].

A method to purify bovine liver xanthine oxidase in described, with which samples of 256-fold specific activity with respect to the initial homogenate are obtained. Bovine liver xanthine oxidase and chicken liver xanthine dehydrogenase with oxygen as electron acceptor exhibit similar profile in pKM and log V versus pH plots. With NAD+ as electron acceptor a different profile in the pKM xanthine plot is obtained for chicken liver xanthine dehydrogenase. However three inflection points at the same pH values appear in all plots. Both enzymes are irreversibly inhibited by pCMB and reversibly by N-ethylmaleimide and by iodoacetamide, with competitive and uncompetitive type inhibitions respectively. These results suggest that NAD+ alters the enzymatic action since its binding to the enzyme antecedes the binding of xanthine to the xanthine oxidase molecule, without undergoing itself any modification. 0.15 M DDT of DTE treatment of bovine liver xanthine oxidase gives to the enzyme a permanent activity with NAD+ without modifying its activity with oxygen. The enzyme thus treated produces parallel straight lines in Lineweaver-Burk plots.

Animals↗
PubMed1979

[Molecular forms of chicken liver cytoplasmic malate dehydrogenase (author's transl)].

Cytoplasmic malate dehydrogenase has been purified 20 -- fold from the supernatant fraction of chicken liver homogenates in 0.25 M sucrose (differential centrifugation at 100,000 x g) through calcium phosphate gel absorption, ammonium sulphate fractionation (45-80% saturation) and Sephadex G-100 chromatography. Two molecular forms, A and B, of the enzyme are unmodified during the purification process, observed by electrophoresis. Two additional bands that appear in the electrophoretic patterns are not attributable to molecular forms of the enzyme, but to the lack of non-dehydrogenase activity of the preparation used. Both forms differ in their thermal stability (form A is more thermolabile) and net charge; and they both have the same molecular weight (67,000 +/- 5,000 daltons), determined by Sephadex G-200 chromatography. The enzyme in the purified preparations exhibits two KM values in the double reciprocal plot v vs [L-malate], due to the presence of two forms with different affinity for the hydroxyacid.

Animals↗
PubMed1978

Kinetic mechanism of the hydroxypyruvate-lactate dehydrogenase-NADH system.

Chicken liver lactate dehydrogenase L-lactate : NAD+ oxidoreductase, EC1.1.1.27) reversibly catalyses the conversion of hydroxypyruvate to L-glycerate. The variation of the initial reaction rate with the substrate or coenzyme (NADH) concentration together with the inhibition caused by the reaction products and excess substrates, reveal that the kinetic mechanism of the reaction, with hydroxypyruvate as substrate, is of the rapid-equilibrium, ordered-ternary-complex type; NADH is the first substrate in the reaction sequence. Rate equations have been developed for the hydroxypyruvate.E.NADH system without inhibitors, with excess substrates, and with reaction products. Comparison of the rate equations obtained with those calculated theoretically from an ordered-ternary-complex mechanism reveals the existence of E.NAD.NADH,E.NAD-hydroxypyruvate and E.hydroxypyruvate complexes.

Animals↗
PubMed1978

[Molecular forms of guanine aminohydrolase (author's transl)].

Guanine aminohydrolase (E.C. 3.5.4.3) has been purified 11-fold from the supernatant fraction of guinea-pig liver homogenates in 0.25 M sucrose (centrifuged at 50,000 X g) through thermic denaturation at 60 degrees C and ammonium sulphate fractionation (30--60% saturation). The enzyme in the homogenates and purified preparations exhibited two Km values. In both preparations four enzymatic electrophoretic bands have been detected. Purified guanine aminohydrolase is chromatographically resolved on DEAE-sephadex in three components whose active forms appeared separately on their pherograms. The enzymatic form eluted at lower ionic strength has the least anodic mobility, is inhibited by guanine (4 X 10(-5) M) and presents only one Km value (1.5 X 10(-5) M). The enzymatic form eluted at greater ionic strength exhibits the highest anodic mobility, is also inhibited by guanine (7 X 10(-5) M) and its Km value seems to be 6.3 X 10(-6) M. Molecular weight of enzymatics forms determined by Sephadex G-200 chromatography, is 120,000 +/- 5,000. The preceding results, correlated with the chromatographic homogeneity of guanine aminohydrolase, purified in Sephadex G-100, suggests that the four molecular forms of the native enzyme may be considered as isozymes.

Aminohydrolases↗