Analyzing the graphs suggest that cinnamic acid is a noncompetitive inhibiter of
tyrosinase’s reaction with L-Dopa. When graphed out, both the slope and y-intercept of
the inhibited data were roughly double that of the uninhibited results. The x-intercept
should be the same if it is noncompetitive, however there is a difference between the two
when using the line equations and setting y=0. The x-int for inhibited was -2481, while
uninhibited it was -3764. Despite this difference, noncompetitive seemed to fit the data
best.
A quick search of cinnamic acid and tyrosinase reveals several previous experiments
which have determined that it is indeed noncompetitive. A link to a French study is
provided below, where the Ki was found to be 1.994 (MUCH higher than our results).
When comparing the Km values found amongst the class, there was a clear difference
between the L and D Dopa values. L-Dopa averaged to .1876 mM while D-Dopa
averaged to 1.359 mM. This indicated a clear preference for the L-Dopa stereoisomer, as
lower Km values means the enzyme and substrate bind together more tightly.
http://cat.inist.fr/?aModele=afficheN&cpsidt=16745827