sweetness, sweet-tasting protein, sweet taste receptor, electrostatic potential, quantum chemical calculation, HOMO, LUMO
Many naturally occurring sweet-tasting proteins have been isolated and are largely expected to be available as a
replacement for natural sugars and artificial sweeteners in the near future. We have carried out a large-scale all-electron
quantum chemical calculation on des-pGlu brazzein, a sweet-tasting protein, and four different mutants by employing a
density functional method program, ProteinDF, in order to examine a relationship between the sweetness of protein
sweeteners and their electronic properties such as electrostatic potential and frontier molecular orbitals, HOMO and
LUMO. ProteinDF all-electron canonical molecular orbital calculations toward des-pGlu brazzein and two different sweettatsting
mutants, Asp29Lys and Glu41Lys, indicated that a number of amino acid residues including neutral amino acids,
Tyr8 and Tyr51, have positive charge and especially for two mutants the positive charge widely spreads over each mutant.
On the other hand, similar all-electron calculations for Arg33Ala and Arg43Ala mutants having a taste like water revealed
that the number of amino acid residues with positive charge in these two mutants is less than that in des-pGlu brazzein and
Asp29Lys and Glu41Lys mutants. In addition, we found that some positively charged amino acid residues occur in the
HOMO and LUMO of des-pGlu brazzein and two sweet-tasting mutants.
JSST2012 International Conference on Simulation Technology
