JBC, Vol. 250, Issue 15, 5818-5825, Aug, 1975
Purification and properties of citrate lyase from Streptococcus diacetilactis
M. Singh and P. A. Srere
Citrate lyase from Streptococcus diacetilactis has been purified to yield a
protein that was homogeneous as judged by sedimentation velocity and
sedimentation equilibrium experiments. The enzyme's sedimentation
coefficient is 16.8 S and its molecular weight is around 585,000. It
contains three nonidentical subunits of about 53,000, 34,000, and 10,000
daltons. The enzyme in its active form contains an acetyl group which turns
over during the citrate cleavage reaction. Removal of the acetyl group
inactivates the enzyme. The deacetyl enzyme can be partially reactivated by
acetylation with acetic anhydride. The enzyme undergoes slow
"reaction-inactivation." The rate of inactivation is first order and the
rate constant of inactivation is much lower than that for a similar
inactivation process of the citrate lyase from Klebsiella aerogenes. Like
the latter enzyme it contains stoichiometric amounts of
phosphopantothenate. The enzyme is inactivated at pH greater than 8.1 and
the presence of citrate provides protection against this inactivation.
Sedimentation studies of the enzyme at pH 8.7 indicate that the enzyme is
dissociated, which may account for the inactivation. The enzyme is
immunologically different from citrate lyases of K. aerogenes and
Escherichia coli.