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Let's do some unit analysis: $\pu t$ = time $\pu U$ = units = $\mathrm{mol_{product}/t}$ $\pu s=$ specific activity $\mathrm{= U/g_{protein}}$ Therefore: $\mathrm{s = mol_{product} / (g_{protien} \times{t})}$ Your sheet says: $\mathrm{k_{cat}= s \times MW_{protien}}$ And we know that: $\mathrm{MW_{protein} = g_{protein} / mol_{protein}}$ ...


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$K_M$ is a constant and is not $V_{\mathrm{max}}/2$ as they have different dimensions. But by the Michaelis Menten equation, $V=\frac{V_{\mathrm{max}}[S]}{K_M+[S]}$. So, when $[S]=K_M$, we have $V=\frac{V_{\mathrm{max}}[S]}{[S]+[S]}=\frac{V_{\mathrm{max}}}{2}$. Hence, $K_M$ is the substrate concentration, at which we would have $V=V_{\mathrm{max}}/2$. ...


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The situation you described is entirely normal. $V_{max}$ is the same, so when described with a graph of initial reaction rate vs. substrate concentration, both curves will asymptotically approach the same maximum level. $K_M$ is higher in one than the other, so the exact shape of the curve as it goes from 0 to $V_{max}$ is different. As you may know, you ...


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The order of magnitude for your intercept value depends on the axis of your graph, which in turn depends on the values / units of your input values. As an example if your substrate concentrations are in the range of $\mu mol / l$ (which is micromolar, not mircomoles), then that is also the order of magnitue you'll get out of the calculation. $dm^{-3}$ ...


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Have you got data for different concentrations of hydrogen peroxode? If so you should choose a time point that falls on the linear part of your time graph. And plot the rate at that time point for each substrate concentration. That will give you a MM curve where you can calculate the values you desire. You cannot calculate them with just your time data ...


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