Steady State Kinetics and Data Analysis Flashcards

Terminology and mathematical models related to enzyme kinetics, focusing on steady-state parameters and various methods of data analysis.

Steady State Assumptions

The conditions required for the Michaelis-Menten equation where [S] > [E]

Michaelis-Menten Equation

$$v_0 = \frac{V_{max}[S]}{K_m + [S]}$$

$$V_{max}$$

The theoretical maximum rate for a given enzyme concentration, occurring when all enzyme is bound to substrate.

$$k_{cat}$$

Also known as the turnover number, it is the catalytic rate constant representing the number of substrate to product conversions per enzyme per unit time ($s^{-1}$).

$$K_m$$

The substrate concentration that gives half maximum velocity ($\frac{V_{max}}{2}$); a smaller value indicates a higher affinity for the substrate.

Specificity Constant

The ratio $\frac{k_{cat}}{K_m}$, which indicates how good an enzyme is by accounting for both substrate affinity and catalytic speed.

Lineweaver-Burk Plot

A double reciprocal linear transformation defined by $\frac{1}{v_0} = \frac{K_m}{V_{max}}\frac{1}{[S]} + \frac{1}{V_{max}}$, famously biased toward low $[S]$ data points.

Hanes-Woolf Plot

A linear transformation where $\frac{[S]}{v_0}$ is plotted against $[S]$, with a slope of $\frac{1}{V_{max}}$ and an x-intercept of $-K_m$.

Eadie-Hofstee Plot

A linear transformation where $v_0$ is plotted against $\frac{v_0}{[S]}$, featuring a slope of $-K_m$ and a y-intercept of $V_{max}$.

Non-linear regression

The preferred modern method for estimating $K_m$ and $V_{max}$ by fitting experimental data directly to the Michaelis-Menten equation rather than using linear transformations.

Which plots are best to analyse INHIBITION

• The Dixon plot (1/V0 vs I)

• The Cornish Bowden ([S]/V0 vs I)

What are the two types of inhibitors

Reversible: temporarily binds to enzymes, activity is restored when inhibitor is displaced

Irreversible: covalently bond, permanently inhibits the reaction

Types of reversible inhibitors

Competitive

Uncompetitive

Mixed

Competitive Inhibitor

Vmax unchanged, Km increases

Uncompetitive inhibitor

Vmax decreases, Km varies

what does kiu=kic show

pure non competitive inhibition (rare)

what type of inhibition does the dixon plot show

competitive

what type of inhibition does the cornish bowden plot show

uncompetitive