Abstract
Brazzein is a small sweet-tasting protein isolated from the fruit of the African plant, Pentadiplandra brazzeana Baillon with potential of replacement of carbohydrate sweeteners. Carbon content analysis was used to examine the effect of mutation in brazzein’s two regions at residues 29–33 and 39–43 with residue 36 reported to be important in sweet tasting of the protein. Analysis for local carbon density at the mutational sites for brazzein mutants with increased sweetness taste at residues 29 and 41 revealed normal carbon distribution curves with increased carbon frequency peak compared to the wild-type, consequently stabilized the local structure. Brazzein mutants with reduced sweetness taste at residue position 30, 33, 36 and 43 were mostly characterized by abnormal broadened distribution curve for carbon content with decreased frequency peak which destabilized the local structure and possibly leading to loss of protein functionality. Further analysis of carbon distribution profile along protein sequences of brazzein revealed a variation in carbon distribution between mutants with increased sweetness taste and those with decreased sweetness taste. Mutants with increased sweetness taste had carbon distribution profile balancing well conforming to the globular proteins which prefers to have 31.45% of carbon all along the sequence for stability. This study has provided further information and additional insights into protein atomic composition in brazzein and its role in understanding the effect of mutation.
Highlights
Brazzein is the smallest sweet-tasting protein consisting of 54 amino-acid residues and four disulfide bonds with a molecular mass of approximately 6.5 kDa, with good stability at high temperatures and over a wide pH range
For residue 29 the carbon distribution at mutational sites D29A, D29N and D29K are given in figure 1
For mutation site D29A the mutant has stretch carbon content in hydrophilic region at 0.257 with considerably increased frequency peak compared to the wild-type which has a stretch of carbon content in hydrophilic region at 0.286
Summary
Brazzein is the smallest sweet-tasting protein consisting of 54 amino-acid residues and four disulfide bonds with a molecular mass of approximately 6.5 kDa, with good stability at high temperatures and over a wide pH range. Brazzein has inherent sweetness 500 to 2000 times that of sucrose on a molar basis with reported different uses such as tastemodifying protein and as an alternative to low calorie sweeteners [3]. There is a high demand for low calorie, protein-based sweeteners with promising taste properties. Occurring sweet and taste modifying proteins are being seen as potential replacements for the carbohydrate sweeteners. Sweetness from carbohydrates such as sugars have several problems associated with their use ranging from tooth decay to diabetes mellitus. As a sweet-tasting protein, brazzein has the potential for replacement sugars, by acting as natural and high-quality sweeteners. Other valuable uses of brazzein include antimicrobial activity against bacteria and the fungus [7]
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