TAILIEUCHUNG - Báo cáo khoa học: Critical molecular regions for elicitation of the sweetness of the sweet-tasting protein, thaumatin I

Thaumatin is an intensely sweet-tasting protein. To identify the critical amino acid residue(s) responsible for elicitation of the sweetness of thau-matin, we prepared mutant thaumatin proteins, usingPichia pastoris,in which alanine residues were substituted for lysine or arginine residues, and the sweetness of each mutant protein was evaluated by sensory analysis in humans. | ễFEBS Journal Critical molecular regions for elicitation of the sweetness of the sweet-tasting protein thaumatin I Keisuke Ohta1 Tetsuya Masuda1 2 Nobuyuki Ide1 and Naofumi Kitabatake1 2 1 Division of Food Science and Biotechnology Graduate Schoolof Agriculture Kyoto University Japan 2 Department of NaturalResources Graduate Schoolof Globaland EnvironmentalStudies Kyoto University Japan Keywords sweetness sweet-tasting protein thaumatin Correspondence N. Kitabatake Division of Food Science and Biotechnology Graduate Schoolof Agriculture Kyoto University Uji Kyoto 611-0011 Japan Fax 81 774 38 3743 Tel 81 774 38 3742 E-mail kitabatake@ Received 31 March 2008 revised 17 April 2008 accepted 15 May 2008 doi Thaumatin is an intensely sweet-tasting protein. To identify the critical amino acid residue s responsible for elicitation of the sweetness of thau-matin we prepared mutant thaumatin proteins using Pichia pastoris in which alanine residues were substituted for lysine or arginine residues and the sweetness of each mutant protein was evaluated by sensory analysis in humans. Four lysine residues K49 K67 K106 and K163 and three arginine residues R76 R79 and R82 played significant roles in thaumatin sweetness. Of these residues K67 and R82 were particularly important for eliciting the sweetness. We also prepared two further mutant thaumatin I proteins one in which an arginine residue was substituted for a lysine residue R82K and one in which a lysine residue was substituted for an arginine residue K67R. The threshold value for sweetness was higher for R82K than for thaumatin I indicating that not only the positive charge but also the structure of the side chain of the arginine residue at position 82 influences the sweetness of thaumatin whereas only the positive charge of the K67 side chain affects sweetness. Thaumatin is a sweet-tasting protein. There are at least five different forms of thaumatin two major forms .

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