Curculin

Curculin is a sweet protein that was discovered and isolated in 1990 from the fruit of Curculigo latifolia (Hypoxidaceae), a plant from Malaysia. Like miraculin, curculin exhibits taste-modifying activity; however, unlike miraculin, it also exhibits a sweet taste by itself. After consumption of curculin, water and sour solutions taste sweet. The plant is referred to locally as 'Lumbah' or 'Lemba'.

Protein structure

The active form of curculin is a heterodimer consisting of two monomeric units connected through two disulfide bridges. The mature monomers each consist of a sequence of 114 amino acids, weighing 12.5 kDa (curculin 1) and 12.7 kDa (curculin 2), respectively. While each of the two isoforms is capable of forming a homodimer, these do not possess the sweet taste nor the taste-modifying activity of the heterodimeric form. To avoid confusion, the heterodimeric form is sometimes referred to as "neoculin".

Amino acid sequence of sweet protein curculin adapted from Swiss-Prot biological database of protein sequences.