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Activation enthalpies and pH dependence of phenol hydroxylase from Trichosporon cutaneum , in vitro and in situ
Author(s) -
Mörtberg Monika,
Neujahr Halina Y.
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)80988-8
Subject(s) - phenol , in situ , in vitro , chemistry , enzyme , kinetics , limiting , catalysis , biochemistry , stereochemistry , organic chemistry , mechanical engineering , physics , quantum mechanics , engineering
The effect of pH and temperature on phenol hydroxylase in vitro was compared to the corresponding effect on the enzyme in situ, in permeabilized cells. Activation enthalpies in situ were about 75–80% of those in vitro, in both cases decreasing with increasing pH (6.0–8.5). The order of addition of phenol and NADPH affected the K m values for phenol at 25°C, but not at 10°C. The results support the idea that the enzyme in situ is in a more favourable position for catalysis than the purified enzyme and that slow conformational changes, triggered by binding of phenol, become rate limiting above 10°C.