Enzyme Kinetics Simulator
Michaelis–Menten, and how inhibitors give themselves away
Tune Vmax, Km, and inhibitor concentration across four inhibition mechanisms, and watch each one produce its own unmistakable signature on a Lineweaver–Burk plot.
The takeaway
You can determine where a drug binds without ever seeing it bind — the geometry of the double-reciprocal plot tells you the mechanism.
Inhibition mechanism
Km apparent
150.0µM
↑ 3.00× vs 50
Vmax apparent
100.0µM/min
= 100% of Vmax
kcat (turnover)
166.7s⁻¹
1.00e+4 substrates · enzyme⁻¹ · min⁻¹
kcat / Km
1.11 × 10⁶M⁻¹s⁻¹
specificity constant
Michaelis–Menten curve
v = Vmax·[S] / (Km + [S])The hyperbola saturates: once every active site is occupied, more substrate buys you nothing. The dashed grey line is the uninhibited reference — the difference between the two curves is the drug's effect.
Inhibition at [S] = Km
50.0%
Surmountable by [S]?
Yes — Vmax recoverable
Intrinsic kcat
166.7 s⁻¹
Lineweaver–Burk (double reciprocal)
1/v = (Km/Vmax)·(1/[S]) + 1/VmaxLinearise the hyperbola and each mechanism leaves a different fingerprint. Watch where the lines cross as you raise [I] — that intersection point is the whole diagnosis.
| Condition | Slope (Km/Vmax) | y-int (1/Vmax) | x-int (−1/Km) |
|---|---|---|---|
| [I] = 0 | 0.500 | 0.0100 | -0.0200 |
| [I] = 20 µM | 1.500 | 0.0100 | -6.67e-3 |
| [I] = 40 µM | 2.500 | 0.0100 | -4.00e-3 |
Competitive signature: Lines share the SAME y-intercept (1/Vmax is untouched) and fan out to different x-intercepts. A shared y-intercept is the fingerprint of competitive inhibition.
Mechanism · Competitive
Where does the inhibitor bind? Free enzyme (E) only — the active site
The inhibitor is a substrate look-alike that occupies the active site of the FREE enzyme. Enzyme and inhibitor compete for the same real estate, so the enzyme merely looks like it has lost affinity — apparent Km rises. Flood the system with substrate and you out-compete the inhibitor: Vmax is fully recoverable. This surmountability is the diagnostic hallmark.
Effect on Km
Km apparent ↑ by α
Effect on Vmax
Vmax unchanged
In the clinic: Methotrexate on dihydrofolate reductase (a folate mimic) and statins on HMG-CoA reductase (an HMG-CoA mimic). Both are active-site rivals.
Why pharma cares
Mechanism of action is not a marketing word — it is a measurement. You run the assay at several [S] and several [I], plot the double reciprocal, and the geometry of the lines tells you whether your molecule sits in the active site or somewhere else entirely.
- →Competitive drugs lose potency when the natural substrate piles up. A competitive kinase inhibitor fights millimolar cellular ATP — which is why cellular IC50 often sits far above the biochemical one.
- →Uncompetitive drugs get stronger where flux is highest, self-targeting overactive tissue. That selectivity is a design goal, not an accident.
- →kcat/Kmis the number to beat: it ranks substrates and caps at ~10⁸–10⁹ M⁻¹s⁻¹, the diffusion limit. An enzyme at that ceiling is "catalytically perfect" — it converts essentially every molecule it meets.
Current specificity constant
3.33 × 10⁶ M⁻¹s⁻¹ uninhibited
1.11 × 10⁶ M⁻¹s⁻¹ apparent