Fig. (5). K_m determination for KinEASE TK substrate with Syk enzyme Various concentrations of Syk enzyme were run using different concentrations of TK substrate-biotin. Michaelis-Menten analysis of results fluorescence yielded a K_m apparent value of 0.1µM TK substrate-biotin. The signal to noise ratio at this concentration of substrate (3.4nM Syk) was 30.7.