Hydrolase

Résumé

Les hydrolases constituent une classe d'enzymes qui catalysent les réactions d'hydrolyse de molécules suivant la réaction générale : On y trouve par exemple

les estérases, qui hydrolysent les esters (R-CO-O~R'),
les peptidases, qui hydrolysent les liaisons peptidiques (AA1-CO~NH-AA2),
les glycosidases, qui hydrolysent les oligo- ou polysaccharides (sucre1-O~sucre2),
les phosphatases, qui hydrolysent les produits phosphorés (exemple : ATP + H2O ⇌ ADP + P). Ces enzymes ne nécessitent pas en général de coenzymes. Elles sont activables par des cations.

On rencontre des hydrolases dans les lysosomes des cellules. Les hydrolases lysosomales, particulièrement acides, présentent un pH d'environ 5 lorsqu'elles sont activées. Elles sont enfermées de façon étanche au sein du lysosome dont la libération brutale du contenu pourrait lyser la cellule. Elles sont classées dans le groupe EC 3 dans la nomenclature EC, et sont réparties en 13 sous-groupes, en fonction du type de liaison qui

Source officielle

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

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Outer membrane lipoprotein NlpI scaffolds peptidoglycan hydrolases within multi-enzyme complexes in Escherichia coli

Ann-Kristin Hov

The peptidoglycan (PG) sacculus provides bacteria with the mechanical strength to maintain cell shape and resist osmotic stress. Enlargement of the mesh-like sacculus requires the combined activity of peptidoglycan synthases and hydrolases. In Escherichia coli, the activity of two PG synthases is driven by lipoproteins anchored in the outer membrane (OM). However, the regulation of PG hydrolases is less well understood, with only regulators for PG amidases having been described. Here, we identify the OM lipoprotein NlpI as a general adaptor protein for PG hydrolases. NlpI binds to different classes of hydrolases and can specifically form complexes with various PG endopeptidases. In addition, NlpI seems to contribute both to PG elongation and division biosynthetic complexes based on its localization and genetic interactions. Consistent with such a role, we reconstitute PG multi-enzyme complexes containing NlpI, the PG synthesis regulator LpoA, its cognate bifunctional synthase, PBP1A, and different endopeptidases. Our results indicate that peptidoglycan regulators and adaptors are part of PG biosynthetic multi-enzyme complexes, regulating and potentially coordinating the spatiotemporal action of PG synthases and hydrolases.

WILEY2020

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Activatable fluorescent probes for hydrolase enzymes based on coumarin-hemicyanine hybrid fluorophores with large Stokes shifts

Kai Johnsson, Mako Kamiya

We show that the equilibrium of intramolecular spirocyclization of coumarin-hemicyanine hybrid fluorophores can be finely tuned by means of chemical modifications. We used this scaffold to develop activatable fluorescent probes with large Stokes shifts for gamma-glutamyltranspeptidase and esterase.

ROYAL SOC CHEMISTRY2020

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Overlapping and essential roles for molecular and mechanical mechanisms in mycobacterial cell division

Haig Alexander Eskandarian, Georg Fantner, Mélanie Thérèse Marie Hannebelle, John McKinney, Adrian Pascal Nievergelt, Pascal Damian Odermatt

Mechanisms to control cell division are essential for cell proliferation and survival. Bacterial cell growth and division require the coordinated activity of peptidoglycan synthases and hydrolytic enzymes to maintain mechanical integrity of the cell wall. Recent studies suggest that cell separation is governed by mechanical forces. How mechanical forces interact with molecular mechanisms to control bacterial cell division in space and time is poorly understood. Here we use a combination of atomic force microscope imaging, nanomechanical mapping and nanomanipulation to show that enzymatic activity and mechanical forces serve overlapping and essential roles in mycobacterial cell division. We find that mechanical stress gradually accumulates in the cell wall, concentrated at the future division site, culminating in rapid (millisecond) cleavage of nascent sibling cells. Inhibiting cell wall hydrolysis delays cleavage; conversely, locally increasing cell wall stress causes instantaneous and premature cleavage. Cells deficient in peptidoglycan hydrolytic activity fail to locally decrease their cell wall strength and undergo natural cleavage, instead forming chains of non-growing cells. Cleavage of these cells can be mechanically induced by local application of stress with an atomic force microscope. These findings establish a direct link between actively controlled molecular mechanisms and passively controlled mechanical forces in bacterial cell division.

2019

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