Pun1-encoded Protein Determines Capsaicin Levels in Capsicum

Capsaicinoids, including capsaicin, are responsible for the pungency of pepper (Capsicum sp.). However, the capsaicin synthesis has not been characterized. Proteins from the putative aminotransferase (pAMT) and Pungent gene 1 (Pun1) are believed to catalyze the final steps in the pathway. Chikara Masuta of Hokkaido University in Japan generated anti-Pun1 antibodies to determine how Pun1 fits in the capsaicin synthesis.

The addition of the anti-Pun1 antibodies in an in vitro capsaicin synthesis inhibited the pathway. In the Pun1-down-regulated tissues, levels of the Pun1 protein as well as capsaicin were reduced. Analysis of pepper cultivars revealed that high levels of capsaicin were accompanied by high expression levels of both pAMT and Pun1.

Further analysis revealed that differing levels of vanillylamine, a precursor of capsaicin, between pungent and non-pungent cultivars. Vanillylamine levels were low in the pungent cultivars, probably due to its rapid conversion to capsaicin, while vanillylamine levels were high in non-pungent cultivars due to the lack of Pun1.

For more information, read the full article in BioMed Central.