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# Lineweaver-Burk Plot of Isozymes

BIOCHM-XI1NOS

Lactate dehydrogenase is an enzyme that exists as isozymes -- that is, different versions of the same enzyme. The reaction catalyzed is shown.

$$\text{pyruvate} \space +\space \text{NADH} \space \xrightarrow [ ]{ } \text{lactate} \space +\space \text{NAD}$$

These isozymes differ slightly in their kinetic constants. The liver isozyme has a Michaelis constant of 10 mM and a Maximal Velocity (${ V }_{ max }$) of 125 nmole/mg protein min, while the muscle version has values of 15 mM and 100 nmole/mg protein min, respectively.

If velocity of these two isozymes is measured over a range of concentrations of NADH, which choice below BEST depicts the Lineweaver-Burk plot?

The liver isozyme is shown in red and the muscle is shown in blue.

A
B
C
D