Please show work The activity of sphingosine kinase was measured in the presence
ID: 484528 • Letter: P
Question
Please show work
The activity of sphingosine kinase was measured in the presence of threo-dihydrosphingosine, a stereoisomer of sphingosine. The Lineweaver-Burk plot obtained from a kinetic analysis of sphingosine kinase activity carried out in the presence of this inhibitor is shown in Figure 19.6.
1. Calculate the Km and Vmax values in the absence and presence of the inhibitor. What kind of an inhibitor is threo-dihydrosphingosine?
0.2 0.1 0.12 y 0.271x 0.011 0.1 0.08 0.06 0.04 0.0580 x 0.0081 0.02 0.2 0.3 0.1 0.4 ISphingos inel m M 1Explanation / Answer
In a lineweaver -Burk plor slope = Km/Vmax and intercept = 1/Vmax
In absence of inhibitor :
1/Vmax = 1/0.0081 = 123.46 nmol/min
Km = 0.058 * 123.46 = 7.16 mM
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In presence of inhibitor:
Vax = 1/0.011 =90.91 mmol/min
Km = 0.271 * 90.91 = 24.64 mmol
As both Km and Vmax decreases, this is an uncompititive inhibitor