How many Km and Vmax values pertain to a bisubstrate reaction? and how many Km and Vmax values pertain to allosteric enzymes?
There is one Vmax and there are 2 Kms for a bisubstrate reaction.
For an allosteric enzyme, one or both of the Kms and/or the Vmax will be altered when the allosteric ligand is bound, resulting in a different set of values from the enzyme with no allosteric ligand bound.
Thank you, Professor Shapiro. And could you kindly tell me if a reaction is multi-step then how many Km and Vmax values it'll pertain?
There is only one Vmax for the forward reaction, and another for the reverse reaction, if it can be run in reverse.
There is one Km for each substrate, and one for each product if the reaction is run in reverse.
If there is an intermediate step in which no substrate binds, there is no Km for it.
For example, the DNA ligase reaction has 2 substrates in the forward direction, but the full reaction sequence has 3 steps. There are only 2 Kms, one for each substrate (ATP or NAD and nicked DNA).
In the case of an enzyme which binds two molecules of the same substrate, there is a separate Km for each of the 2 molecules. An example is D-Ala-D-Ala ligase, which binds 2 molecules of D-Alanine.
Dear sir,
For an allosteric enzyme, one or both of the Kms and/or the Vmax will be altered when the allosteric ligand is bound, resulting in a different set of values from the enzyme with no allosteric ligand bound.
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