Km z Km is the [S] at 1/2 Vmax z Km is a constant for a given enzyme z Km is an estimate of the equilibrium constant for S binding to E z Small Km means tight binding; high Km means weak binding KM is a measure of [S] required for effective catalysis to occurKm z Km is the [S] at 1/2 Vmax z Km is a constant for a given enzyme z Km is an estimate of the equilibrium constant for S binding to E z Small Km means tight binding; high Km means weak binding KM is a measure of [S] required for effective catalysis to occur