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Steady-state kinetics of carboxypeptidase Y, a proteinase from yeast, were studied by using the reaction of 4-nitrophenyl trimethylacetate as a probe. The pH profile of kcat. is sigmoidal in H2O-based buffers for the carboxypeptidase Y-catalysed hydrolysis of this ester (kcat. referring to the rate of deacylation of trimethylacetyl-carboxypeptidase Y). The corresponding pD profile in 2H2O is doubly sigmoidal, with inflexions at pD approximately 3.8 and approximately 6.8. The ionization of pKDapp. approximately 3.8 is caused by a rapid inactivation in 2H2O media by a process that is only slowly reversed on transfer to pH 7.00 phosphate buffer in H2O. The corresponding inactivation in H2O-based buffers of low pH is considerably slower (approximately 30-fold), follows a first-order rate-dependence and is very strongly pH-dependent, indicating some form of co-operative change in enzyme tertiary structure.
W T Chang, and
K T Douglas
May 1978,
Experientia,
W T Chang, and
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October 1978,
Archives internationales de physiologie et de biochimie,
W T Chang, and
K T Douglas
August 1981,
Journal of bacteriology,
W T Chang, and
K T Douglas
January 2015,
Biotechnology letters,
W T Chang, and
K T Douglas
October 1993,
Bioscience, biotechnology, and biochemistry,
W T Chang, and
K T Douglas
February 2003,
Current genetics,
W T Chang, and
K T Douglas
August 1982,
Biochimica et biophysica acta,
W T Chang, and
K T Douglas
January 2000,
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W T Chang, and
K T Douglas
July 1998,
Applied microbiology and biotechnology,
W T Chang, and
K T Douglas
September 2007,
Biochimica et biophysica acta,
