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A Baici

Publications and source records attributed to A Baici.

64 records · Page 4Linked to original sources
PubMed1979

[Chronic polyarthritis: role of polymorphonuclear leukocytes in the destruction of pannus-free articular cartilage].

The synovial fluid (SF) of RA patients contains large amounts of PMN which are well equipped with neutral enzymes to degrade articular cartilage: elastase and cathepsin G, which both destroy proteoglycans and native collagen, as well as 2 types of collagenoases. Indirect evidence suggests that PMN might be important in the destruction of RA articular cartilage. In 19 SF of RA patients no free elastase or collagenase was found. Using immune histochemical methods, we observed that PMN and macrophages of SF contain both elastase and alpha 1-anti-trypsin and alpha 2-macroglobulin. Peripheral PMN - but not monocytes - contain elastase, however both types of cells lack alpha 1-antitrypsin and alpha 2-macroglobulin. Elastase is demonstratable in the superficial layer of pannus free RA articular cartilage. These findings suggest that neutral proteinases from PMN in RA SF are generally neutralized by physiologic inhibitors and removed by phagocytes. The enzyme-inhibitor interaction might be bypassed during "frustrated phagocytosis" so that enzymes like PMN elastase can damage RA articular cartilage.

Arthritis, Rheumatoid↗
PubMed1978

Fluorescence properties of reduced thionicotinamide--adenine dinucleotide and of its complex with octopine dehydrogenase.

Reduced 3-thionicotinamide--adenine dinucleotide (sNADH) is shown to be fluorescent, with an emission maximum at 510 nm when excited in the region of the absorption maximum (398 nm), and with a very low quantum yield, (3.4 +/- 0.5) x 10(-4). The interaction between sNADH and octopine dehydrogenase was investigated by ultraviolet-difference spectroscopy and fluorescence. Some surprising fluorescence features were found when sNADH was bound to the enzyme in the presence of D-octopine, as follows. (a) There is an unusually high enhancement of the dinucleotide fluorescence (by at least a factor of 100) attended by a 40-nm blue shift of the emission maximum. (b) The protein fluorescence is quenched almost completely. (c) The bound coenzyme analog undergoes a photoreaction, which proceeds differently from that occurring the free form. These features appear to be unique to the octopine.sNADH complex, as for example they are not present when sNADH is bound to horse liver alcohol dehydrogenase, or when NADH is bound to octopine dehydrogenase. The possible origin of these fluorescence features is discussed. Binding and kinetic studies were carried out with sNAD and sNADH. It was found that sNAD neither binds nor acts kinetically as a coenzyme. sNADH exhibits relatively good binding, with Km and Ki values close to those of the natural coenzyme, but the turnover number is 460 times smaller than that with NADH. The kinetic consequences of these findings are discussed. The sNADH dissociation constants were determined as a function of temperature, and appear to be practically temperature-independent in the range 10--40 degrees C. It seems thus, in agreement with previous studies, that the interaction between octopine dehydrogenase and coenzymes proceeds athermically, regardless of the structure, affinity, and chemical reactivity of the coenzyme. The possible biological and chemical meaning of this finding is discussed.

Amino Acid Oxidoreductases↗
PubMed1975

Investigations on the kinetic mechanism of octopine dehydrogenase. 2. Location of the rate-limiting step for enzyme turnover.

The kinetic mechanism of octopine dehydrogenase has been investigated by stopped-flow and isotope replacement techniques. When the enzyme is saturated by substrate and coenzyme, both for NADH oxidation and NAD+ reduction, the stationary phase is preceded by a rapid burst. Under these saturation conditions, furthermore, the stationary phase shows a secondary isotope effect when 4S-[4(2)H]NADH is substituted for NADH and when (on the other reaction end) D-[2H] octopine is substituted for D-octopine. The data are taken to indicate that the rate-limiting step for enzyme turnover is a step following a very fast chemical transformation of the reagents. However, when the substrate concentration is lowered below the corresponding Km value keeping the coenzyme concentration at saturating levels, the time course of the reaction shows no burst and the stationary phase has a larger isotope effect. This indicated that under those non-saturating conditions, the enzyme turnover has a larger contribution than the hydrogen-transfer step. Changing the coenzyme concentration alone has very little or no effect on the amplitude of the burst or on the isotope effect. These features are discussed in terms of the other known kinetic properties of the enzyme, and in terms of analogous studies reported in the literature for other dehydrogenases.

Animals↗
PubMed1975

Relationship between fluorescence and conformation of epsilonNAD+ bound to dehydrogenases.

This work reports on the interaction of the fluorescent nicotinamide 1,N6-ethenoadenine dinucleotide (epsilonNAD+) with horse liver alcohol dehydrogenase, octopine dehydrogenase, and glyceraldehyde-3-phosphate dehydrogenase from different sources (yeast, lobster muscle, and rabbit muscle). The coenzyme fluorescence is enhanced by a factor of 10-13 in all systems investigated. It is shown that this enhancement cannot be due to changes in the polarity of the environment upon binding, and that it must be rather ascribed to structural properties of the bound coenzyme. Although dynamic factors could also be important for inducing changes in the quantum yield of epsilonNAD+ fluorescence, the close similarity of the fluorescence enhancement factor in all cases investigated indicates that the conformation of bound coenzyme is rather invariant in the different enzyme systems and overwhelmingly shifted toward an open form. Dissociation constants for epsilonNAD+-dehydrogenases complexes can be determined by monitoring the coenzyme fluorescence enhancement or the protein fluorescence quenching. In the case of yeast glyceraldehyde-3-phosphate dehydrogenase at pH 7.0 and t = 20 degrees the binding plots obtained by the two methods are coincident, and show no cooperativity. The affinity of epsilonNAD+ is generally lower than that of NAD+, although epsilonNAD+ maintains most of the binding characteristics of NAD+. For example, it forms a tight complex with horse liver alcohol dehydrogenase and pyrazole, and with octopine dehydrogenase saturated by L-arginine and pyruvate. One major difference in the binding behavior of NAD+ and epsilonNAD+ seems to be present in the muscle glyceraldehyde-3-phosphate dehydrogenase. In fact, no difference was found for epsilon NAD+ between the affinities of the third and fourth binding sites. The results and implications of this work are compared with those obtained recently by other authors.

Alcohol Oxidoreductases↗
PubMed1975

Temperature-determined enzymatic functions in octopine dehydrogenase.

We investigated the temperature dependence of several functions of octopine dehydrogenase, a monomeric enzyme extracted from the shell fish Pecten maximus L. We found that six enzymatic functions are temperature independent or change only negligibly with temperatue. These are the dissociation constants of three coenzyme complexes and the Michaelis Km values for NAD, NADH and one of the substrates (D-octopine). This is taken as an indication of a temperature-regulatory mechanism which enables the enzyme to maintain a constant level of NAD, NADH and D-octopine in binary and ternary complexes independent of fluctuations of the external temperature. This is discussed with reference to enzymes from other poikilotherms, which reportedly display similar biologically meaningful response to temperature. We also discuss the meaning of our data from a thermodynamic viewpoint. Considering that in a temperature-independent binding process only entropy changes contribute to the standard free-energy change, we speculate on possible molecular models which might account for our results. We also investigate the activation-energy parameters for the reaction catalyzed by octopine dehydrogenase, as obtained from the temperature dependence of V. It is found that octopine dehydrogenase, relative to other dehydrogenases, is provided with a rather low delta H not equal to, which enables the enzyme to change its turnover number by only a small factor in the temperature range 5--35 degrees C.

Amino Acid Oxidoreductases↗
PubMedDate not supplied

Inhibition of human lysosomal elastase by the cartilage bone marrow extract Rumalon.

Human lysosomal elastase from polymorphonuclear leucocytes is inhibited by the cartilage bone marrow extract Rumalon. Separately, both the cartilage and the bone marrow extracts are able to inhibit the enzymatic activity by 73%, under saturating conditions. The mixture of the two extracts inhibits elastase by 93%. It is suggested that the two partners act as a cumulative inhibition mechanism and this phenomenon is emphasized in a general theoretical model for synergy of proteinase-directed inhibitors.

Arthritis, Rheumatoid↗
PubMedDate not supplied

Inhibition of extracellular matrix-degrading endopeptidases: problems, comments, and hypotheses.

A critical analysis of research on inhibitors of extracellular matrix-degrading endopeptidases reveals that a great number of substances could potentially be used for therapeutic purposes. There are, however, many obstacles that hinder this objective. If the problems are due to the characteristics of the inhibitors, they can possibly be circumvented by chemical methods, but if they are innate properties of the pathological environment and of the mode of action of the enzymes, the problem may not have an immediate solution.

Animals↗