Insight into broad substrate specificity and synergistic contribution of a fungal α-glucosidase in Chinese Nong-flavor daqu

Table 1 The kinetic hydrolysis of various substrates by NFAg31A

Substrate	Main linkage/monomer	K_m(mM)	k_cat(1/s)	k_cat/K_m(1/(s*mM))	Specific activity(U/mg)
pNPαG	α-(1→4)-glucose	0.55 ± 0.06	0.10 ± 0.00	0.19	0.053 ± 0.001
Maltose	α-(1→4)-glucose	11.5 ± 0.7	4.4 ± 0.1	0.39	0.38 ± 0.01
Maltotriose	α-(1→4)-glucose	nd^a	nd^a	0.59 ± 0.04^b	0.83 ± 0.00
Maltotetraose	α-(1→4)-glucose	nd^a	nd^a	0.85 ± 0.04^b	0.60 ± 0.06
Maltopentaose	α-(1→4)-glucose	nd^a	nd^a	0.37 ± 0.03^b	0.24 ± 0.02
Soluble Starch	α-(1→4)-α-(1→6) glucose	nd^a	nd^a	14.2 ± 0.6^b	2.40 ± 0.24
Nigerose	α-(1→3)-glucose	19.3 ± 2.5	29.3 ± 2.1	1.52	1.59 ± 0.02
Kojibiose	α-(1→2)-glucose	3.9 ± 0.3	3.2 ± 0.1	0.82	0.63 ± 0.03
Isomaltose	α-(1→6)-glucose	nd^a	nd^a	0.0014 ± 0.0001^b	0.0017 ± 0.0001
Sucrose	glucose-α-(1→2)-fructose	-	-	-	No activity

^a: The kinetic hydrolysis of those substrates did not fit very well to the Michaelis-Menten equation and the enzyme was not saturated with the substrate under detected concentrations, thus their kinetic values did not determine here
^b: The k_cat/Km values were determined at sufficiently low substrate concentration, by the relationship k_cat/Km = v/([S][E]), which is valid for [S] < < Km.

ISSN: 1475-2859