Table 2.

Steady state kinetic parameters of human tyrosine hydroxylase isoforms^a

Enzyme	Ktyr (μM)b	K6MPH4 (μM)c	Vmax (min−1)
hTyrH1	77 ± 10	116 ± 10	135 ± 7
hTyrH2	66 ± 5	75 ± 6	100 ± 2
hTyrH3	79 ± 9	70 ± 9	119 ± 5
hTyrH4	73 ± 6	63 ± 5	108 ± 3

^aConditions: 100 μg/mL catalase, 1 mM dithiothreitol, 10 μM ferrous ammonium sulfate, 50 mM HEPES, pH 7.0, 32°C.

^b400 μM 6MPH₄.

^c200 μM tyrosine.