Abstract
When both purified γ-glutamyl transpeptidase and cysteine sulfoxide lyase were added to the homogenate of Shiitake mushroom, formaldehyde amounted to twice that found in the control. On the other hand, the enzymatic formation of formaldehyde was terminated in the presence of either a serine-borate mixture or hydroxylamine. It has been proved that a significant amount of formaldehyde is liberated from lentinic acid and its component “des-Glu-lentinic acid” by the action of flavor enzymes. Des-Glu-lentinic acid, a new sulfur-containing amino acid, which served as a specific substrate for C-S lyace, evolved a maximum amount of formaldehyde in the range of pH 8 to 9. A C-S lyase found in Lentinus edodes showed a high affinity towards the amino acid giving an apparent Michaelis constant of 60 to 70 μM. Experimental results evidenced that the spontaneous evolution of formaldehyde in L. edodes is entrusted to the pathway of the lenthionine production from lentinic acid.
