TABLE 3.

Kinetic constants for exo-β-d-galactofuranosidase-catalyzed hydrolysis of substrates^a

Substrate	Km (mM)	kcat (s−1)	kcat/Km (M−1 s−1)
pP2GMii	0.80	14	1.7 × 104
pP25GMii	>1.5	ND	1.7 × 103b
β-d-Galf(5,6)	0.10	41	4.1 × 105
β-d-Galf(3,4)	0.25	43	1.7 × 105
1-O-Methyl-β-Galf	2.6	29	1.1 × 104

^aAbbreviations: β-Gal_f(5,6), mixture of penta- and hexa-β-(1→5)-d-galactofuranooligosaccharides with a DP of 5.5; β-d-Gal_f(3,4), mixture of tri- and tetra-β-d-(1,5)-galactofuranooligosaccharides with a DP of 3.4; 1-O-Methyl-β-Gal_f, 1-O-methyl-β-d-galactofuranoside. ND, not determined. The concentration of nonreducing terminal galactofuranosyl residues in pP_xGMⁱⁱ was calculated based on the percentage of galactofuranosyl in the total carbohydrate of the polymer and the ratio of total galactose to nonreducing terminal galactofuranosyl residues. The enzyme activities were referenced to 25 U mg⁻¹ with 1-O-methyl-β-d-galactofuranoside as a substrate. Apparent K_m and k_cat were determined from Cornish-Bowden–Wharton plots (11). The k_cat was calculated based on an enzyme molecular mass of 70 kDa. 

^bThe k_cat/K_m for the exo-βd-galactofuranosidase-catalyzed depolymerization of pP₂₅GMⁱⁱ was estimated from the slope of the first order region of the curve for the initial velocity versus the nonreducing terminal galactofuranosyl-pP₂₅GMⁱⁱ concentration.