Properties
of the induced acid phosphatase and of the
constitutive acid phosphatase of Euglena
Bennun, A. and Blum, J.J.
The induced acid phosphatase (EC 3.1.3.2) of Euglena gracilis
has been solubil¬ized and partially purified. The enzyme
has a wide range of substrate specificity and, as predicted
from earlier studies on whole cells, the ratio of its activity
at pH 5 to its activity at pH 7 in presence of 5 mM fluoride
is 1.1 for p-nitrophenylphosphate as substrate. The enzyme
is competitively inhibited by arsenate and phosphate, but
exhibits mixed competitive–non-competitive inhibition with
molybdate. The enzyme migrates towards the cathode when electrophoresis
is performed on cellulose acetate strips at pH 8.2. Euglena
also contains several other acid phosphatases. The two major
constitutive acid phosphatases, which remain particle-bound
after a variety of extraction procedures, differ in their
thermal stability from each other and from the induced phosphatase.
The ratio of activity at pH 5 to the activity at pH 7 plus
5mM fluoride for the mixture of these two constitutive enzymes
is 15. These observations establish that the increase in acid
phosphatase activity occurring in Euglena in response to phosphate
deprivation is due to the synthesis of a separate enzyme.
The heat of thermal inactivation of the purified induced enzyme
is about four times larger than the heat of denaturation computed
from the effect of temperature on the rate of reversion of
the induced phosphatase in vivo.
Biochimica et Biophysica Acta, 128, (1966), 106-123