TABLE 1.

Substrate specificity of recombinant α-glucosidases (AglH) from Thermus thermophilus strains HB27, HB8, and GK24

Substrate	Glycosidic linkage	Glucose released (μmol/min·mg protein)a
		AglHHB27	AglHHB8	AglHGK24
Disaccharides
α,α-Trehalose	O-α-d-Glucosyl-(1→1)-d-glucose	126 ± 5.3	0.0	0.0
α,β-Trehalose	O-α-d-Glucosyl-(1→1)-β-d-glucose	49 ± 3.6	0.0	0.0
β,β-Trehalose	O-β-d-Glucosyl-(1→1)-β-d-glucose	0.0	0.0	0.0
Kojibiose	O-α-d-Glucosyl-(1→2)-d-glucose	26 ± 3.1	31 ± 3.3	38 ± 4.7
Sucrose	O-α-d-Glucosyl-(1→2)-β-d-fructose	10 ± 1.1	9 ± 4.1	67 ± 3.4
Nigerose	O-α-d-Glucosyl-(1→3)-d-glucose	20 ± 1.1	36 ± 8.1	56 ± 2.2
Turanose	O-α-d-Glucosyl-(1→3)-d-fructose	18 ± 3.6	28 ± 3.5	3 ± 3.4
Maltose	O-α-d-Glucosyl-(1→4)-d-glucose	12 ± 0.2b	3.1 ± 0.2b	1.8 ± 0.1b
Cellobiose	O-β-d-Glucosyl-(1→4)-d-glucose	0.0	0.0	0.0
Leucrose	O-α-d-Glucosyl-(1→5)-d-fructose	9.3 ± 0.4	14 ± 2.1	14 ± 0.8
Isomaltose	O-α-d-Glucosyl-(1→6)-d-glucose	80 ± 3.6	108 ± 5.9	113 ± 7.7
Palatinose	O-α-d-Glucosyl-(1→6)-d-fructose	41 ± 1.6	45 ± 6.7	40 ± 1.4
Gentiobiose	O-β-d-Glucosyl-(1→6)-d-glucose	0.0	0.0	0.0
Melibiose	O-α-d-Galactosyl-(1→6)-d-glucose	0.0	0.0	0.0
Trisaccharides
Melizitose	O-α-d-Glucosyl-(1→3)-β-d-fructosyl-(2→1)-d-glucose	0.0	0.0	0.0
Maltotriose	O-α-d-Glucosyl-(1→4)-α-d-glucosyl-(1→4)-d-glucose	18 ± 3.7b	8.3 ± 1.2b	5.8 ± 0.8b
Raffinose	O-α-d-Galactosyl-(1→6)-α-d-glucosyl-(1→2)-β-d-fructose	0.0	0.0	0.0
Panose	O-α-d-Glucosyl-(1→6)-α-d-glucosyl-(1→4)-d-glucose	45 ± 0.2	45 ± 5.8	50 ± 2.7
Isomaltotriose	O-α-d-Glucosyl(1→6)-α-d-glucosyl-(1→6)-d-glucose	38 ± 4.5	49 ± 8.2	5 ± 4.5

^aActivity was determined with 0.5 μg of pure enzymes and 10 mM of each substrate at 70°C for 20 min, except where indicated otherwise.

^bActivity was determined with 4 μg of pure enzymes and 100 mM of each substrate at 70°C for 1 h.