Gl. Mendz et al., IN-SITU CHARACTERIZATION OF HELICOBACTER-PYLORI ARGINASE, Biochimica et biophysica acta. Protein structure and molecular enzymology, 1388(2), 1998, pp. 465-477
The properties of Helicobacter pylori arginase activity in metabolical
ly competent cells and lysates were investigated with the aim of obtai
ning a better understanding of the nitrogen metabolism of the bacteriu
m. One-dimensional H-1- and C-13-nuclear magnetic resonance spectrosco
py, spectrophotometry, radio tracer analysis and protein purification
techniques were employed to characterize in situ the first step in the
utilization of L-arginine by the bacterium. Arginase activity was ass
ociated with the cell-envelope fraction obtained by centrifugation of
lysates. A K-m of 22 +/- 3 mM was determined for the enzyme activity,
and differences of V-max were observed between strains. Divalent catio
ns stimulated arginase activity, and the most potent activators were C
o2+>Ni2+>Mn2+. The activity was highly specific for L-arginine and did
not catabolize analogs recognized by other arginases of prokaryote an
d eukaryote origin. The K-i of several inhibitors was measured and ser
ved also to characterize the enzyme activity. The presence of bicarbon
ate enhanced the hydrolysis of L-arginine in cell suspensions, but not
in lysates or semi-purified enzyme preparations. Amino acid sequence
analyses revealed important differences between the deduced structures
of H. pylori arginase and those of other organisms. This finding was
consistent with experimental data which showed that H. pylori arginase
has unique properties. (C) 1998 Elsevier Science B.V. All rights rese
rved.