Enzyme Kinetics Lab

Substrate concentration [S] 60

Km — affinity 1.00

kcat — turnover rate 1.20

Enzyme count [E] 10

Measured V

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Theoretical V

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Saturation

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Products formed

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How it works

Each amber enzyme has one active site. Grey substrate spheres wander the chamber by Brownian motion; when one drifts close enough to a free active site it can bind, forming a transient ES complex (the substrate snaps to the enzyme and glows blue). After a randomized dwell — averaging 1/kcat — the enzyme converts it to product (green), releases it, and becomes free again. The freed substrate slot re-diffuses in a moment later, holding [S] roughly constant, exactly as a real initial-rate assay does.

E + S ⇌ ES → E + P
V = Vmax·[S] / (Km + [S])
Vmax = kcat·[E]total

[S] — substrate concentration (particle count in the chamber). Raising it pushes more collisions per second, driving the measured rate up toward Vmax as sites saturate.
Km — the substrate level at half-maximal velocity; a low Km means a "stickier" enzyme that binds substrate readily even when [S] is small, so the curve saturates earlier.
kcat — how fast a bound complex converts to product; it sets Vmax together with the enzyme count, and shortens how long each active site stays occupied.
[E] — total enzyme sites available; scales Vmax linearly since each site turns over substrate independently.

Real-world relevance: this is the same experiment biochemists run to characterize a new enzyme or drug target — vary [S], record initial rates, and fit Km/Vmax to compare catalytic efficiency (kcat/Km) between variants or inhibitor conditions.

Free substrate ES complex Product Enzyme (free)

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