C. Hellio et Y. Legal, HISTIDINE UTILIZATION BY THE UNICELLULAR ALGA DUNALIELLA-TERTIOLECTA, Comparative biochemistry and physiology. Part A, Molecular & integrative physiology, 119(3), 1998, pp. 753-758
The unicellular alga Dunaliella tertiolecta was cultivated axenically
with histidine, or ammonium, histidine and ammonium ions as nitrogen s
ources. In the presence of histidine as the sole source of nitrogen, c
ell growth is comparable to that observed with the same concentration
of nitrogen in ammonium form. In the presence of both histidine and am
monium, histidine degradation is observed only when the concentration
of ammonium falls below 4 mM. Under these conditions, the first two en
zymes of histidine degradation pathway, histidase and urocanase, as we
ll as histidine permease, are produced. Linear relationships are obser
ved between histidase and urocanase and histidase and histidine permea
se, respectively, showing that, in D. tertiolecta enzyme, systems are
coordinately regulated. Histidase activity is also controlled by succi
nate, glutamate and acetate as carbon sources. D. tertiolecta is unabl
e to grow on a medium containing acetate and histidine together in the
absence of ammonium. (C) 1998 Elsevier Science Inc.