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-pyrophosphate (PRPP) in red blood cells is markedly increased. It has been shown that the red blood cell activity of PRPP synthetase is about three times normal, although the amount of the enzyme protein present is normal. Upon studying the kinetic parameters it was found that the 
was normal but that the 
was three times normal.
This has been interpreted to mean that the catalytic process, as opposed to the binding of substrate, is altered. These two processes are separate stages of the overall catalytic process.
A second example of a clinical finding which is related to the is the hypersensitivity to alcohol that some Asians exhibit. It has long been known that, upon drinking even small amounts of alcohol, some Chinese and Japanese show facial flushing and tachycardia. It is also known that the enzyme alcohol dehydrogenase generates acetaldehyde which is converted to acetate by aldehyde dehydrogenase. The latter enzyme normally exists in two forms, a high affinity (low ) form and a low affinity (high ) form. The people who are sensitive to alcohol lack the high affinity form and as a result the acetaldehyde builds up and cause vasodilation.
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