Table 2.

Kinetic parameters for WT, Y75C, and I99C β-tryptase tetramers, I99C/Y75A/Y37bA dimer, and I99C*/Y75A/Y37bA monomer

Assays were run as described under “Experimental procedures” in the presence of 100 μg/ml heparin. Data were analyzed as described under “Experimental procedures.” Kinetic constants are mean ± S.E.

β-Tryptase	Statea	Km	kcatb	kcat/Kmb	Mutant/WT catalytic efficiencyb,c
		μm	s−1	m−1 s−1
WTd	T	470 ± 60	87 ± 10	1.8 ± 0.1 × 105	1
Y75Cd	T	320 ± 50	37 ± 10	1.2 ± 0.2 × 105	0.63
I99Cd	T	820 ± 30	50 ± 10	0.61 ± 0.1 × 105	0.33
I99C/Y75A/Y37bAe	D	1000 ± 80	5.8 ± 0.3	0.06 ± 0.04 × 105	0.029
I99C*/Y75A/Y37bAf	M	1600 ± 300	6.7 ± 0.7	0.04 ± 0.02 × 105	0.021

^a Data refer to oligomeric state when assayed; T is tetramer; D is dimer; M is monomer.

^b Data were normalized to monomer (protomer).

^c Refers to k_cat/K_m (mutant)/k_cat/K_m (WT).

^d Concentrations of these tetrameric tryptases were 1 nm; protomer concentrations were 4 nm.

^e Concentrations of dimeric tryptase were 100 nm; protomer concentrations were 200 nm.

^f Concentrations of monomeric tryptase were 400 nm.