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Regulation of urease by urea and its precursors in the lichen Evernia prunmtri
Author(s) -
PérezUrria E.,
Vicente C.
Publication year - 1985
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1985.tb08669.x
Subject(s) - urease , urea , chemistry , incubation , putrescine , hydrolysis , ammonia , nitrogen , arginine , biochemistry , enzyme , amino acid , organic chemistry
Thallus samples of £. prunastri (L.) Adi, floated on 40 mM urea developed urease (EC 3.5.1.5.) activity which levelled off after 6h. L‐Arguiine, L‐ornitfaine and patrescine added to the incubation media intitially enhanced the effect of urea, but the urease activity ceased after 4h of incubation in the presence of the latter two compounds or when L‐arginine was used; as the sole source of nitrogen. This decline in activity was observed after 6h when L‐arginine was added to urea‐containing media. The loss of urease activity is thought to result from the synthesis of repressers in the presence of the amino acids, whereas putrescine appears to affect membrane permeability by increasing the uptake of urea by the cells. Declining urease activity in the latter case would then be due to feedback inhibition caused by the excess of ammonia produced in both hydrolysis of urea and oxidation of putrescine.