83.
Summary Lyophilized and stored in a deep-freeze, the mycelial material was found to retain
cis-aconitic decarboxylase activity unimpaired at the end of 2 months. Mycelia could be stored also in the frozen condition but after squeezing hard to remove as much of adherent water as possible. Extracts with maximum
cis-aconitic decarboxylase activity were obtained when the frozen or better the lyophilized mycelia of
Aspergillus terreus were ground in a mortar with phosphate buffer using pyrex glass powder as abrasive.
Cis-aconitic decarboxylase was purified 25-fold by fractionation with ammonium sulfate, starting from extracts of the mycelia in phosphate buffer. The purified enzyme was considerably more stable than the crude extracts to storage and dialysis. The optimum pH was 5.8 using 0.2
m phosphate buffer; Km value was 5×10
-3
m at pH 5.8 and 37°C. EDTA and 8-hydroxyquinoline activated the enzyme; all metals tested inhibited the enzyme, Zn
++ and Cu
++ leading to complete inactivation. Fluoride, arsenite and azide also inhibited the enzyme activity.
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