Distribution and Activation of Chitin Synthase in Protoplast Fractions Released during the Lytic Digestion of Aspergillus nidulans Hyphae

Abstract

SUMMARY: Protoplasts were produced from Aspergillus nidulans mycelium using Trichoderma lytic enzyme. The influence of KC1 and MgSO4as stabilizer systems on the morphological variation of protoplasts produced during digestion and the pattern of release from hyphae were compared. The results suggest that protoplast release in the presence of KC1 followed a sequential fractionation of the hyphae with ‘early’ protoplasts originating from the tip regions and ‘late’ protoplasts from the distal regions. In MgSO4-stabilized systems the hyphae were disrupted in a less ordered fashion. Between 12 and 16% of the mycelial protein was recovered in protoplast form using the systems described. The level of chitin synthase (EC 2.4.1.16) and the capacity for trypsin-activation of the enzyme in protoplast fractions was investigated. In KC1-stabilized systems, ‘early’ (1 h) fractions possessed higher specific activities than later fractions. Activatable enzyme was low in the early fraction but was present at high levels in later fractions. It is suggested that these observations are consistent with a model relating active and activatable enzyme to hyphal growth.