A. Penyige et al., MODIFICATION OF GLUTAMINE-SYNTHETASE IN STREPTOMYCES-GRISEUS BY ADP-RIBOSYLATION AND ADENYLYLATION, Biochemical and biophysical research communications, 204(2), 1994, pp. 598-605
Addition of NH4+ to Streptomyces griseus 2682 cells grown in NO3-conta
ining medium resulted in a rapid decline in glutamine synthetase activ
ity due to covalent modification of the enzyme. The NH4+ promoted inac
tivation of the enzyme was inhibited by the ADP-ribosyltransferase inh
ibitor 3-methoxybenzamide. In the presence of ADP-ribosyltransferase a
ctivity the purified glutamine synthetase was also inhibited by NAD(+)
in a concentration-dependent manner. ADP-ribosylation of glutamine sy
nthetase was demonstrated in vitro by showing the incorporation of lab
eled ADP-ribose from [alpha-P-32]NAD(+) into glutamine synthetase subu
nits. Beside ADP-ribosylation, adenylylation of glutamine synthetase w
as also shown in S. griseus since phosphodiesterase I treatment reacti
vated the enzyme in crude extracts of NH4+-shocked cells. Glutamine sy
nthetase was also inhibited and modified by ATP in crude cellular extr
acts. These results suggest that in S. griseus 2682 ADP-ribosylation o
f glutamine synthetase could be an alternative modification to adenyly
lation to regulate glutamine synthetase activity. (C) 1994 Academic Pr
ess, Inc.