The principle of Dixon (1965) has been extended to give rapid graphical methods for determining enzyme constants for substrates (Km) and inhibitors (Ki). It does away with the sometimes questionable assumption that the amounts of substrate or inhibitor bound by the enzyme are negligible in comparison with the total amount added, and is therefore valid even for cases of high affinity, where the usual methods fail. Besides doing away with the need for calculation, it enables the concentrations of the various components of the system to be read off directly for any point of the velocity curve.

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