Purification and characterisation of two enzymes related to endogenous formaldehyde in Lentinula edodes

In this study, γ-glutamyl transpeptidase (GGT) and l-cysteine sulphoxide lyase (C-S lyase) were purified from the fruiting body of Lentinula edodes in three steps and then characterised. We found that GGT together with C-S lyase caused the generation of endogenous formaldehyde in L. edodes. GGT was composed of a large subunit of 41 kDa and a small subunit of 25 kDa, and C-S lyase was composed of two identical subunits of 46 kDa, as determined by SDS-PAGE. GGT was stable at pH 8.0-10.0 with an optimum pH of 8.8, and was stable at 20-50°C with an optimum activity at 37°C. C-S lyase was stable at pH 8.0-9.0 with an optimum pH of 8.5, and was stable at 20-60°C with an optimum activity at 40°C. The present work supports the study of the mechanism of endogenous formaldehyde in L. edodes.