•Plotting Vi as a
function of [S], we find that
•At low values of [S],
the initial velocity,Vi, rises almost linearly with increasing [S].
•But as [S] increases,
the gains in Vi level off (forming a rectangular hyperbola).
• The asymptote
represents the maximum velocity of the reaction, designated Vmax
• The substrate concentration that produces a
Vi that is one-half of Vmax is
designated the Michaelis-Menten
constant, Km(named after the
scientists who developed the study of enzyme kinetics).
•Km is (roughly) an
inverse measure of the affinity or strength of binding between the enzyme and its substrate. The lower
the Km, the greater the affinity (so
the lower the concentration of substrate needed to achieve a given rate).