MHETase

MHETase ( Ideonella sakaiensis )
	Structure of MHETase PDB 6QGA with the non-hydrolyzable substrate analog MHETA
	Existing structural data: see UniProt
Mass / length primary structure	63 kDa / 596 amino acids
Secondary to quaternary structure	α / β hydrolase, family of tannases
Identifier
External IDs	UniProt : A0A0K8P8E7 ;
Enzyme classification
EC, category	3.1.1.102 , esterase
Response type	Hydrolysis of aromatic esters
Substrate	MHET ( mono- (2-hydroxyethyl) terephthalic acid , mono-hydroxyethyl terephthalate)
Products	Terephthalic acid and ethylene glycol
Occurrence
Parent taxon	Bacteria ›Proteobacteria› Betaproteobacteria ›Burkholderiales› Ideonella

The MHETase enzyme is a hydrolase that was discovered in 2016 and has the property of breaking down mono- (2-hydroxyethyl) -terephthalic acid produced by the PETase enzyme into ethylene glycol and terephthalic acid . The enzyme was created through natural evolution and is found in the bacterium Ideonella sakaiensis , which was also discovered in 2016 .

Chemical reaction

The first enzyme in PET degradation, PETase , splits the plastic into the intermediate product MHET ( mono- (2-hydroxyethyl) -terephthalic acid ) and small amounts of BHET ( bis- (2-hydroxyethyl) -terephthalic acid ). MHETase hydrolyzes the ester linkage of MHET to form terephthalic acid and ethylene glycol .

In addition to the natural substrate MHET, the chromogenic substrate MpNPT, mono-p-nitrophenyl terephthalate, is converted well, which can be used to determine the enzymatic activity. Ferulic acid esters and gallic acid esters, the substrates of the closest relatives of the tannase family, are not converted. p-Nitrophenyl esters of aliphatic monocarboxylic acids such as the most widely used esterase substrate p-nitrophenyl acetate are also not converted.

structure

The structure was clarified in 2019 and shows the widespread folding of an α / β hydrolase . According to the classification in the ESTHER database, the MHETase in block X belongs to the tannase family, which mainly contains tannases and feruloyl esterases. In addition to the hydrolase domain, which is common to all α / β-hydrolase enzymes, MHETase has a large lid domain ('lid'), which is responsible for the substrate specificity. The residues of the catalytic triad, Ser225, His528 and Asp492, are in the hydrolase domain, while the residues Arg411, Ser416 and Ser419 in the lid domain, with their hydrogen bonds to the carboxylate group, are essential for the specificity of terephthalic acid esters.

MHETase with bound MHETA (cf. Fig. 2a in). Short distances between the non-hydrolyzable substrate analog MHETA (mono-hydroxyethyl-terephthalamide, N- (2-hydroxyethyl) -terephthalic acid monoamide in green) and the catalytic residues Ser225, His528 and Asp492 (part of the hydrolase domain in brown) or residues that bind the ligands ( Part of the lid domain in blue) are shown as a dashed line. The 2FoFc electron density around MHETA at 1.5 sigma is shown as a blue network. PDB: 6QGA

Web links

ESTHER database

Individual evidence

↑ ^a ^b ^c S Yoshida, K Hiraga, K Takehana, I Taniguchi, H Yamaji, Y Maeda, K Toyohara, K Miyamoto, Y Kimura, K Oda: A bacterium that degrades and assimilates poly (ethylene terephthalate) . In: Science . 351, No. 6278, March 2016, pp. 1196–9. doi : 10.1126 / science.aad6359 . PMID 26965627 .
↑ Michael: First plastic-degrading bacterium discovered. Spektrum.de, March 16, 2016, accessed April 8, 2016 .
↑ ^a ^b ^c ^d Gottfried J. Palm, Lukas Reisky, Dominique Böttcher, Henrik Müller, Emil AP Michels, Miriam C. Walczak, Leona Berndt, Manfred Weiss, Uwe Bornscheuer, Gert Weber: Structure of the plastic-degrading Ideonella sakaiensis MHETase bound to a substrate . In: Nature Communications . 10, No. 1, April 2019, ISSN 2041-1723 , p. 1717-. doi : 10.1038 / s41467-019-09326-3 .
^ L Renault, V Nègre, T Hotelier, X Cousin, P Marchot, A Chatonnet: New friendly tools for users of ESTHER, the database of the alpha / beta-hydrolase fold superfamily of proteins . In: Chem. Biol. Interact. . 157-158, December 2005, pp. 339-43. doi : 10.1016 / j.cbi.2005.10.100 . PMID 16297901 .

[Yoshida_2016-1] S Yoshida, K Hiraga, K Takehana, I Taniguchi, H Yamaji, Y Maeda, K Toyohara, K Miyamoto, Y Kimura, K Oda: A bacterium that degrades and assimilates poly (ethylene terephthalate) . In: Science . 351, No. 6278, March 2016, pp. 1196–9. doi : 10.1126 / science.aad6359 . PMID 26965627 .

[2] Michael: First plastic-degrading bacterium discovered. Spektrum.de, March 16, 2016, accessed April 8, 2016 .

[Palm_NatureCommunications_2019-3] Gottfried J. Palm, Lukas Reisky, Dominique Böttcher, Henrik Müller, Emil AP Michels, Miriam C. Walczak, Leona Berndt, Manfred Weiss, Uwe Bornscheuer, Gert Weber: Structure of the plastic-degrading Ideonella sakaiensis MHETase bound to a substrate . In: Nature Communications . 10, No. 1, April 2019, ISSN 2041-1723 , p. 1717-. doi : 10.1038 / s41467-019-09326-3 .

[pmid16297901-4] L Renault, V Nègre, T Hotelier, X Cousin, P Marchot, A Chatonnet: New friendly tools for users of ESTHER, the database of the alpha / beta-hydrolase fold superfamily of proteins . In: Chem. Biol. Interact. . 157-158, December 2005, pp. 339-43. doi : 10.1016 / j.cbi.2005.10.100 . PMID 16297901 .