Studies on a 2, 3-diaminopropionate: Ammonia-lyase from a pseudomonad.

2,3-Diaminopropionate:ammonia-lyase,
an induced enzyme in a Pseudomonas isolate,
has been purified 40-fold and found to be homogeneous
by disc gel electrophoresis and by ultracentrifugation.
Some of its properties have been
studied. The optimum pH and temperature for
activity are 8 and 40 degree c, respectively. The enzyme
shows a high degree of substrate specificity,
acting only on 2,3-diaminopropionate; the D-isomer
is only one-eighth as effective as the L-form.
L-Homoserine and DL-cystathionine are not substrates,
and 3-cyanoalanine does not inhibit its
activity. It is a pyridoxal phosphate enzyme
which requires free enzyme sulphhydryls for activity.
The Kmvalues for L-2,3-diaminopropionate
and pyridoxal phosphate are 1mM and 25uM, respectively.
The molecular weight of the enzyme is
about 80000 as determined by gel ftltration. On
treatment with 0.5M urea or guanidine hydrochloride,
the enzyme dissociates into inactive subunits
with an approximate molecular weight of 45000.
One mole of the active enzyme binds one mole of
pyridoxal phosphate. The bacterial enzyme seems
to be quite different in many of its properties
from the rat liver enzyme which also exhibits
the substrate specificity of cystathionine lyase.