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.