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Concept

Enzyme digestive

Résumé

Une enzyme digestive a pour fonction de dégrader les macromolécules biologiques en libérant les petites unités moléculaires (monomères) qui les constituent afin de faciliter leur assimilation par l'organisme. Ces enzymes se trouvent d'une part dans l'appareil digestif humain, dans celui des animaux et dans les pièges des plantes carnivores, où elles participent à la digestion de la nourriture, et d'autre part à l'intérieur même des cellules, essentiellement dans un organite appelé lysosome, où elles participent au métabolisme cellulaire en permettant le recyclage des biomolécules. Il existe un grand nombre d'enzymes digestives. On en trouve dans la salive, où elles sont produites par les glandes salivaires, dans l'estomac, où elles sont produites dans la paroi stomacale, dans le suc pancréatique, où elles sont produites par le pancréas exocrine, et dans les intestins (intestin grêle et gros intestin). On les classe en fonction du type de substrats qu'elles dégradent :

les peptidase

Source officielle

https://fr.wikipedia.org/wiki/Enzyme_digestive

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Concepts associés (56)

vignette|Système digestif. La digestion est un mode de transformation mécanique et chimique des aliments en nutriments assimilables ou non par l'organisme. Par définition, la digestion est un proces

Le système digestif, appelé aussi appareil digestif, est l'ensemble des organes qui chez les êtres vivants a pour rôle d'assurer l'ingestion et la digestion des aliments pour en extraire l'énergie et

Le pancréas, prononcé , est un organe situé dans l'abdomen des vertébrés, au niveau du rétropéritoine, en avant de l'aorte et de la veine cave inférieure et en arrière de l'estomac. C'est un organe

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Redefining the metabolic landscape through TGF-beta/Activin signaling in Drosophila melanogaster

Wen Bin Chng

Multicellular organisms assess their nutritional state and adapt their metabolic landscape to match their energy demands. In this thesis, we address a longstanding conundrum of how an organism coordinates digestive enzyme expression in response to its nutritional status. Hydrolysis of food materials by endogenous or microbial-derived digestive enzymes precedes absorption through the gut lumen. Thus, modulation of endogenous digestive mechanism represents a pragmatic step to limit the uptake of nutrients when nutrients are in abundance. In Drosophila melanogaster, it is known that dietary glucose represses amylase transcript and enzymatic activity, in a process known as glucose repression. Here, we show that glucose reduces the expression of many carbohydrases, lipases, and glucose transporters, presumably to prevent nutritional overload after feeding. We found that the repression of carbohydrases is effected by nutritious sugars through the induction of the TGF-beta ligand, Dawdle. Interestingly, glucose repression of digestive enzymes is dependent upon the induction of Dawdle in the fat body, a tissue functionally analogous to the mammalian liver and adipose tissue. Dawdle is then transported via the circulation to activate TGFÎ²/Activin signaling in the midgut, leading to the repression of digestive enzymes expression. We later discovered that Dawdle expression in the fat body is regulated by the evolutionarily conserved Mio-bigmax transcription factor complex. In addition, expression of Dawdle must be tightly coordinated to reflect the nutritional state of adult flies, as flies overexpressing Dawdle are sensitive to starvation and have their TAG and glycogen stores rapidly depleted upon nutrient limitation. Thus, our results are consistent with a model whereby fat body derived Daw functions as a nutritional cue for carbohydrates to modulate metabolic responses in distal tissues. Its induction provides the nutritional signal to repress carbohydrate digestive capacity and stimulate peripheral insulin signaling. In conclusion, our study identifies the TGFÎ²/Activin signaling as a critical mechanism for carbohydrate homeostasis. Our results indicate that the fat body functions as a carbohydrate sensing tissue, which through the secretion of the TGFÎ² ligand, Daw, regulates organism-wide carbohydrate metabolism. Our work in Drosophila is likely to have a broader scientific impact by placing a pathway known for its role in development, immunity, and cancer, as an integral component for sugar sensing and metabolism.

EPFL2015

Chargement

, , ,

We report the discovery of a series of new drug leads that have potent activity against Mycobacterium tuberculosis as well as against other bacteria, fungi, and a malaria parasite. The compounds are analogues of the new tuberculosis (TB) drug SQ109 (1), which has been reported to act by inhibiting a transporter called MmpL3, involved in cell wall biosynthesis. We show that 1 and the new compounds also target enzymes involved in menaquinone biosynthesis and electron transport, inhibiting respiration and ATP biosynthesis, and are uncouplers, collapsing the pH gradient and membrane potential used to power transporters. The result of such multitarget inhibition is potent inhibition of TB cell growth, as well as very low rates of spontaneous drug resistance. Several targets are absent in humans but are present in other bacteria, as well as in malaria parasites, whose growth is also inhibited.

Amer Chemical Soc2014

Chargement

Transforming Growth Factor beta/Activin Signaling Functions as a Sugar-Sensing Feedback Loop to Regulate Digestive Enzyme Expression

Maroun Bou Sleiman, Wen Bin Chng, Bruno Lemaitre

Organisms need to assess their nutritional state and adapt their digestive capacity to the demands for various nutrients. Modulation of digestive enzyme production represents a rational step to regulate nutriment uptake. However, the role of digestion in nutrient homeostasis has been largely neglected. In this study, we analyzed the mechanism underlying glucose repression of digestive enzymes in the adult Drosophila midgut. We demonstrate that glucose represses the expression of many carbohydrases and lipases. Our data reveal that the consumption of nutritious sugars stimulates the secretion of the transforming growth factor beta (TGF-beta) ligand, Dawdle, from the fat body. Dawdle then acts via circulation to activate TGF-beta/Activin signaling in the midgut, culminating in the repression of digestive enzymes that are highly expressed during starvation. Thus, our study not only identifies a mechanism that couples sugar sensing with digestive enzyme expression but points to an important role of TGF-beta/Activin signaling in sugar metabolism.

Elsevier2014

Chargement

Redefining the metabolic landscape through TGF-beta/Activin signaling in Drosophila melanogaster

Wen Bin Chng

EPFL2015