Inactivation of enzymes by inert gas bubbling. A kinetic study.
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Animals↗
Biomedical subjects
M Caussette
Publications and source records attributed to M Caussette.
The self catalytic enzyme inactivation induced by solvent stirring: a new example of protein conformational change induction.
This article gives a new example of the protein conformational change induction. A well known example widely described in the literature is the prion, a protein whose the pathologic form, PrPsc, induces a conformational change of the normal form, PrPc, by interaction with it. This work highlights the existence of a self-catalytic conformation change for lysozyme. The functional modification of this protein is analysed in terms of irreversible loss of activity. Our experiments and the kinetic model derived from our results show that lysozyme inactivation is catalyzed by the inactivated lysozyme molecules; the lysozyme molecules with modified conformation induce a conformational change of native lysozyme molecules that in turn become inactive. This phenomenon is enhanced by stirring, which increases the probability and the efficiency of collisions between enzyme molecules. Furthermore, the self-catalytic inactivation kinetics of lysozyme is increased when salts are dissolved in the enzyme solution. Under these conditions, the protective effect due to the addition of salts, reported in previous literature, disappear. Salt-induced lysozyme destabilization effect can be observed. The salts enhance the aggregation of inactive enzyme molecules. A kinetic model of self catalytic inactivation of the enzyme has been developed, taking into account the results obtained with and without the addition of salts in aqueous solution.
Enzyme Activation↗
Experimental colitis alters visceromotor response to colorectal distension in awake rats.
The influence of intermittent colorectal distension (CRD) on proximal colonic motility and abdominal pain perception was investigated in awake rats equipped with intraparietal electrodes on the cecum, proximal colon, and abdomen, before and three days after rectocolitis induction by trinitrobenzene sulfonic acid (TNB)/ethanol. The normal myoelectrical activities of cecum and proximal colon [5.2 +/- 0.5 and 9.7 +/- 0.7 long spike bursts (LSB) per 5 min, respectively] were significantly (P < 0.05) and gradually decreased by control CRD, at diameters above 9 mm. At the maximum CRD diameter (13.7 mm), 1.6 +/- 0.6 cecal and 3.9 +/- 0.8 colonic spike bursts occurred per 5 min (respectively, 69 and 60% decreases). This upstream inhibition was accompanied by a significant (P < 0.05) and gradual increase in abdominal contractions (0.4 +/- 0.4 per 5 min in control vs 23.4 +/- 1.9 in response to 13.7 mm in diameter). Three days after TNB/ethanol, visceromotor and abdominal responses were significantly (P < 0.05) enhanced at the least CRD diameter of 9 mm (cecum: 3.1 +/- 0.4 after TNB vs 5.0 +/- 0.7 in control; proximal colon: 5.1 +/- 0.9 vs 9.3 +/- 2.2; abdomen: 7.7 +/- 1.5 vs 0.5 +/- 0.4). We conclude that in awake rats, CRD evokes both abdominal contractions in response to pain and inhibition of cecal and proximal colonic motility, which thresholds are both lowered by TNB-induced rectocolitis.
Abdominal Muscles↗
A multifunction and programmable computerized barostat.
A new computerized barostat allowing digestive tone measurement but also programmed distensions is described. The apparatus consists of a pump, driven by a computer, which injects or aspirates air in a flacid bag placed in a part of the gastrointestinal tract when relaxation or contraction occurs. Several parameters can be programmed for tone measurement: mean pressure, window pressure and air flow rate. Isovolumic or isobaric distensions can be performed using three modes: linear, stepwise or step by step with intermediate deflation. The height (mL or mmHg) of the steps and the duration of the distensions and the deflations can also be programmed. Three automatic and one manual safety systems are included. In comparison with previously described barostats the main feature of this apparatus is that it is entirely computerized and can be used for programmed distensions.
Atropine↗