Modification of the Sweetness and Stability of Sweet-Tasting Protein Monellin by Gene Mutation and Protein Engineering

Table 1

Sweetness threshold and maximum heat resistance temperature of monellin and its variants.

Name	Sweetness threshold (μg/mL)	Maximum heat resistance temperature (°C)
Sucrose	10000 ± 150	—
MNEI	0.8 ± 0.05	65
P10A	3.0 ± 0.4	70
F11A	2.0 ± 0.25	70
T12A	10 ± 1.1	55
N14A	0.9 ± 0.1	70
L15A	2.0 ± 0.2	45 ± 5
K17A	>450	<40
F18A	0.9 ± 0.05	55 (50)
A19E (insoluble)	—	—
V20A	2.5 ± 0.5	45
D21A	1.0 ± 0.2	65 (45)
E22A	2.0 ± 0.3	60
E23A	0.8 ± 0.1	85
N24A	0.9 ± 0.15	75 (70)
I26A	0.8 ± 0.05	70 ± 5
C41A	0.5 ± 0.05	70

The protein thermostability was expressed as the maximum heat resistance temperature at which the protein displayed completely denaturation. The temperature in brackets indicated that protein was only partially denatured at this temperature. —: undetected.