<title>Abstract</title><italic>Sphingobium</italic> 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 <italic>ligD</italic>, <italic>ligL</italic>, and <italic>ligN</italic>. The ether linkages of the resulting MPHPV enantiomers are cleaved by stereoselective glutathione (GSH) <italic>S</italic>-transferases (GSTs) encoded by <italic>ligF</italic>, <italic>ligE</italic>, and <italic>ligP</italic>, generating (β<italic>R/</italic>β<italic>S</italic>)-α-glutathionyl-β-hydroxypropiovanillone (GS-HPV) and guaiacol. To date, it has been shown that the gene products of <italic>ligG</italic> and SLG_04120 (<italic>ligQ</italic>), both encoding GST, catalyze GSH removal from (β<italic>R/</italic>β<italic>S</italic>)-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<italic>R</italic>)-GS-HPV than that for (β<italic>S</italic>)-GS-HPV, whereas purified LigQ showed an approximately six-fold higher specific activity for (β<italic>S</italic>)-GS-HPV than that for (β<italic>R</italic>)-GS-HPV. Analyses of mutants of <italic>ligG</italic>, <italic>ligQ</italic>, and both genes revealed that SYK-6 converted (β<italic>R</italic>)-GS-HPV using both LigG and LigQ, whereas only LigQ was involved in converting (β<italic>S</italic>)-GS-HPV. Furthermore, the disruption of both <italic>ligG</italic> and <italic>ligQ</italic> 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.