Table 1.

Kinetic parameters for the hydrolysis of [pyroGlu‐3H]‐TRH by wild‐type and mutant rat TRH‐DE. Specific activities were determined at 2 µm substrate concentration. Reactions were carried out as described under Experimental procedures, values are the mean ± SD from at least three independent transfections. ND, not detected.

Enzyme	Specific activity (nmol·min−1·mg−1)	K m (µm)	V max (nmol·min−1·mg−1)	V max/K m (mL·min−1·mg−1)
Wild‐type	250 ± 44	32.5 ± 1	3727 ± 104	114.67
C68S	210 ± 36	29.3 ± 0.4	2900 ± 489	98.97
C174S	6.25 ± 0.2	–	–	–
C279S	24.56 ± 4.15	27 ± 4	238 ± 51	10.48
C338S	46.38 ± 5.11	33 ± 3	716 ± 28.27	21.69
C444S	4.37 ± 2	–	–	–
C823S	ND	–	–	–
C830S	ND	–	–	–
C859S	9.37 ± 1.37	–	–	–
C895S	ND	–	–	–