Roles of two glutathione S-transferases in the final step of the β-aryl ether cleavage pathway in Sphingobium sp. strain SYK-6

• Published in: Scientific reports Vol. 10; no. 1; p. 20614
• Main Authors: Higuchi, Yudai, Sato, Daisuke, Kamimura, Naofumi, Masai, Eiji
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 26.11.2020; Nature Publishing Group
• Subjects: 631/326/2522; 631/326/41/1969; 631/443/319; 631/45/607/1172; Aromatic compounds; Bacterial Proteins - metabolism; Carbon; Catalysis; Dehydrogenases; Enantiomers; Enzymes; Ether - metabolism; Genes; Glutathione; Glutathione - metabolism; Glutathione Transferase - metabolism; Guaiacol; Humanities and Social Sciences; Lignin; Lignin - metabolism; multidisciplinary; Oxidation; Oxidation-Reduction; Science; Science (multidisciplinary); Sphingobium; Sphingomonadaceae - metabolism; Stereoisomerism; Stereoisomers; Substrate Specificity - physiology; Syk protein
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-77462-8

Sphingobium sp. strain SYK-6 is an alphaproteobacterial degrader of lignin-derived aromatic compounds, which can degrade all the stereoisomers of β-aryl ether-type compounds. SYK-6 cells convert four stereoisomers of guaiacylglycerol-β-guaiacyl ether (GGE) into two enantiomers of α-(2-methoxyphenoxy)-β-hydroxypropiovanillone (MPHPV) through GGE α-carbon atom oxidation by stereoselective Cα-dehydrogenases encoded by ligD , ligL , and ligN . The ether linkages of the resulting MPHPV enantiomers are cleaved by stereoselective glutathione (GSH) S -transferases (GSTs) encoded by ligF , ligE , and ligP , generating (β R/ β S )-α-glutathionyl-β-hydroxypropiovanillone (GS-HPV) and guaiacol. To date, it has been shown that the gene products of ligG and SLG_04120 ( ligQ ), both encoding GST, catalyze GSH removal from (β R/ β S )-GS-HPV, forming achiral β-hydroxypropiovanillone. In this study, we verified the enzyme properties of LigG and LigQ and elucidated their roles in β-aryl ether catabolism. Purified LigG showed an approximately 300-fold higher specific activity for (β R )-GS-HPV than that for (β S )-GS-HPV, whereas purified LigQ showed an approximately six-fold higher specific activity for (β S )-GS-HPV than that for (β R )-GS-HPV. Analyses of mutants of ligG , ligQ , and both genes revealed that SYK-6 converted (β R )-GS-HPV using both LigG and LigQ, whereas only LigQ was involved in converting (β S )-GS-HPV. Furthermore, the disruption of both ligG and ligQ was observed to lead to the loss of the capability of SYK-6 to convert MPHPV. This suggests that GSH removal from GS-HPV catalyzed by LigG and LigQ, is essential for cellular GSH recycling during β-aryl ether catabolism.