Changes in Chitin and N-Acetylglucosamine Contents and Chitinolytic Enzyme Activities during te Growth of Flammulina velutipes Fruit-bodies.

Abstract

We studied the changes in chitin and N-acetylglucosamine(GlcNAc)contents and activities of chitinase and β-N-acetylglucosaminidase(β-GlcNAcase)during the fruit-body development of Flammulina uelutipes (Enokitake) which is one of the important edible mushrooms in Japan. The strain used (IFO7777) formed a matured fruit-body in liquid culture in 25 days. The chitin components of the fungus were 1.0-1.5%in dry mycelia and 2.0-4.0% in dry fruit-bodies, though both components were lower than that of the other fungi of basidiomycotina. The former components linearly increased during the mycelial growth, but when the fruit-body formation began, the increase was considerably suppressed. On the other hand, the amounts of GlcNAc in the culture filtrate and mycelia suddenly decreased at the stage of rapid growth of the fruit-body. It is, therefore, suggested that GlcNAc as a substrate is supplied from them for the synthesis of chitin in the fruit-body. Chitinase activity in mycelia increased at the growing stage of vegetative mycelia, but it was suppressed with the beginning of rapid development of fruit-body. However its high activity continued until the maturation of the fruit-body. The activity in the culture filtrate continuously increased until the maturation of the fruit-body. β-GlcNAcase activity showed a diererent pattern from that of chitinase, that is, the β-GlcNAcase activity in the mycelia decreased with the growth of the fruit-body, whereas that in the culture filtrate increased with the growth. β-GlcNAcase prepared from both mycelia and culture filtrate were partially purified by isoelectrofocusing chromatography and their characteristics were investigated.