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What is kcat km in enzyme kinetics?

It is a measure of how many bound substrate molecules turnover or form product in 1 second. The constant kcat/Km is also referred to as the specificity constant in that it describes how well an enzyme can differentiate between two different competing substrates.

How does kcat affect km?

Most of the time Kcat just equals K2 (NOT the case when there are more reaction steps). Kcat/Km represents the rate of the reaction at negligible substrate concentration. Or in other words, Kcat/Km is the (pseudo-)second order rate constant between the enzyme and the substrate, when [S]≪Km[S]≪Km.

What does kcat depend on?

9. Another important parameter of enzymes is called Kcat (also called turnover number). Kcat is equal to Vmax/[Enzyme]. Because the concentration of enzyme is taken into account in this equation, Kcat does NOT vary with the amount of enzyme used and is therefore a constant for an enzyme.

What does a lower kcat mean?

turnover number

How do you calculate kcat?

Note: the enzyme concentration is the same for all of the test tubes; only the substrate concentrations vary in the assay. Divide the Vmax (from Section 2, Step 4) by the enzyme concentration (from Section 2, Step 5). The result is the value of Kcat.

What is the relationship between turnover number and k2?

At this point we define the turnover number: the number of substrate molecules catalyzed per second per enzyme molecule when the enzyme is saturated with substrate (Nelson and Cox, 2005; Becker et al., 2006). Hence, when the enzyme is saturated with substrate the turnover number (k2) becomes rate limiting.

What do you mean by turnover?

Turnover is the total sales made by a business in a certain period. It’s sometimes referred to as ‘gross revenue’ or ‘income’. This is different to profit, which is a measure of earnings.

How do you calculate km on a graph?

From the graph find the maximum velocity and half it i.e. Vmax/2. Draw a horizontal line from this point till you find the point on the graph that corresponds to it and read off the substrate concentration at that point. This will give the value of Km.