TABLE 3.

Thermodynamic parameters for BuSGBP-B, BfSGBP-B, DgSGBP-B, and BuSGBP-C obtained by isothermal titration calorimetry at 25°C in 50 mM sodium phosphate buffer (pH 7.0)

Carbohydrate	Ka (M−1)				ΔG (kcal · mol−1)				ΔH (kcal · mol−1)				TΔS (kcal · mol−1)
	BuSGBP-B	BfSGBP-B	DgSGBP-B	BuSGBP-C	BuSGBP-B	BfSGBP-B	DgSGBP-B	BuSGBP-C	BuSGBP-B	BfSGBP-B	DgSGBP-B	BuSGBP-C	BuSGBP-B	BfSGBP-B	DgSGBP-B	BuSGBP-C
XyGa	3.0 (±0.5) × 106	3.7 (±0.5) × 105	1.3 (±0.2) × 106	Weakb	−8.3	−7.6	−8.3	Weakb	−31.2 ± 0.5	−33.8 ± 0.8	−44.4 ± 0.7	Weakb	−22.9	−26.2	−36.1	Weak
tamXyGO2	1.6 (±0.1) × 105	2.1 (±0.1) × 105	1.5 (±0.2) × 105	6.8 (±0.1) × 104	−7	−7.2	−7.2	−6.6	−31.1 ± 0.7	−25.3 ± 0.2	−35.7 ± 0.2	−21.8 ± 0.2	−24.1	−18.1	−28.5	−15.2
tamXyGO1	6.4 (±1.0) × 104	6.0 (±0.1) × 103	1.8 (±0.1) × 104	8.6 (±0.6) × 103	−7	−5.1	−5.8	−5.3	−27.7 ± 2.9	−35.8 ± 0.5	−29.2 ± 0.3	−26.5 ± 3.8	−20.7	−30.7	−23.4	−21.2
lettXGO1 cognate GH5	0.67 (±0.04) × 103	2.6 (±0.2) × 103	1.0 (±0.1) × 103	Weakb	−3.9	−4.6	−4.2	Weakb	−70.4 ± 3.9	−26.7 ± 1.2	−118	Weakb	−66.5	−22.1	−113.8	Weak

^aBinding thermodynamics for XyG were based on the concentration of the binding unit, tamXyGO₂. All error values correspond to errors from model fitting to ITC data.

^bWeak binding represents a K_a of 500 M⁻¹.