Aspartokinase of a lysine producing mutant of Micrococcus glutamicus

Aspartokinase from Micrococcus glutamicus AEC RN-13-6/1 [a homoserine
requiring, S-(2–aminoethyl)-L-cysteine resistant, lysine producing strain] was purified 71 fold.
The partially purified enzyme was inhibited by L-lysine. L-threonine, L-methionine, Lisoleucine,
L-valine and L-phenylalanine activated the enzyme and reversed the inhibition by Llysine.
Aspartokinase activity was not derepressed by growth–limiting concentrations of Lthreonine
and/or L–methionine. It was not repressed by an excess of L-lysine (20 mM) and/or
L-isoleucine (15.3 mM). The degree of activation or inhibition by amino acids was dependant
on the composition of the growth medium. This observation is in contrast with the enzyme
from the original (non–lysine–producing) strain which was inhibited by lysine or threonine and
in a concerted manner by threonine plus lysine.